📜  查找所有皇后在棋盘上攻击国王的情况

📅  最后修改于: 2021-05-14 02:22:38             🧑  作者: Mango

给定一个2D数组Queens [] [] ,该数组由8 * 8棋盘中的N个皇后的坐标和表示国王坐标的数组king []组成,任务是找到攻击国王的皇后

例子:

方法请按照以下步骤解决问题:

  • 遍历数组Queens [] []
  • 对于遍历的每个坐标,检查攻击国王的所有可能性,即水平,垂直和对角线。如果发现正在攻击国王,请检查以下内容:
    • 如果没有其他女王从该方向进攻国王,包括当前的国王作为进攻者。
    • 如果该方向已经存在攻击者,请检查当前女王/王后是否是最近的攻击者。如果被发现是真的,包括仙女皇作为攻击者。否则,请继续下一个坐标。
  • 最后,打印所有坐标。

下面是上述方法的实现:

C++
// C++ Program to implement
// the above approach
 
#include 
using namespace std;
 
// Function to find the queen
// closest to king in an
// attacking position
int dis(vector ans,
        vector attacker)
{
    return abs(ans[0] - attacker[0])
           + abs(ans[1] - attacker[1]);
}
 
// Function to find all the queens
// attacking the king in the chessboard
vector > findQueens(
    vector >& queens,
    vector& king)
{
    vector > sol;
    vector > attackers(8);
 
    // Iterating over the coordinates
    // of the queens
    for (int i = 0; i < queens.size(); i++) {
 
        // If king is horizontally on
        // the right of current queen
        if (king[0] == queens[i][0]
            && king[1] > queens[i][1]) {
 
            // If no attacker is present
            // in that direction
            if ((attackers[3].size() == 0)
 
                // Or if the current queen is
                // closest in that direction
                || (dis(attackers[3], king)
                    > dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[3] = queens[i];
        }
 
        // If king is horizontally on
        // the left of current queen
        if (king[0] == queens[i][0]
            && king[1] < queens[i][1]) {
 
            // If no attacker is present
            // in that direction
            if ((attackers[4].size() == 0)
 
                // Or if the current queen is
                // closest in that direction
                || (dis(attackers[4], king)
                    > dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[4] = queens[i];
        }
 
        // If the king is attacked by a
        // queen from the left by a queen
        // diagonal above
        if (king[0] - queens[i][0]
                == king[1] - queens[i][1]
            && king[0] > queens[i][0]) {
 
            // If no attacker is present in
            // that direction
            if ((attackers[0].size() == 0)
 
                // Or the current queen is
                // the closest attacker in
                // that direction
                || (dis(attackers[0], king)
                    > dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[0] = queens[i];
        }
 
        // If the king is attacked by a
        // queen from the left by a queen
        // diagonally below
        if (king[0] - queens[i][0]
                == king[1] - queens[i][1]
            && king[0] < queens[i][0]) {
 
            // If no attacker is present in
            // that direction
            if ((attackers[7].size() == 0)
 
                // Or the current queen is
                // the closest attacker in
                // that direction
                || (dis(attackers[7], king)
                    > dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[7] = queens[i];
        }
 
        // If the king is attacked by a
        // queen from the right by a queen
        // diagonally above
        if (king[1] - queens[i][1] == 0
            && king[0] > queens[i][0]) {
 
            // If no attacker is present in
            // that direction
            if ((attackers[1].size() == 0)
 
                // Or the current queen is
                // the closest attacker in
                // that direction
                || (dis(attackers[1], king)
                    > dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[1] = queens[i];
        }
 
        // If the king is attacked by a
        // queen from the right by a queen
        // diagonally below
        if (king[1] - queens[i][1] == 0
            && king[0] < queens[i][0]) {
 
            // If no attacker is present in
            // that direction
            if ((attackers[6].size() == 0)
 
                // Or the current queen is
                // the closest attacker in
                // that direction
                || (dis(attackers[6], king)
                    > dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[6] = queens[i];
        }
 
        // If a king is vertically below
        // the current queen
        if (king[0] - queens[i][0]
                == -(king[1] - queens[i][1])
            && king[0] > queens[i][0]) {
 
            // If no attacker is present in
            // that direction
            if ((attackers[2].size() == 0)
 
                // Or the current queen is
                // the closest attacker in
                // that direction
                || (dis(attackers[2], king)
                    > dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[2] = queens[i];
        }
 
        // If a king is vertically above
        // the current queen
        if (king[0] - queens[i][0]
                == -(king[1] - queens[i][1])
            && king[0] < queens[i][0]) {
 
            // If no attacker is present in
            // that direction
            if ((attackers[5].size() == 0)
 
                // Or the current queen is
                // the closest attacker in
                // that direction
                || (dis(attackers[5], king)
                    > dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[5] = queens[i];
        }
    }
 
    for (int i = 0; i < 8; i++)
        if (attackers[i].size())
            sol.push_back(attackers[i]);
 
    // Return the coordinates
    return sol;
}
 
// Print all the coordinates of the
// queens attacking the king
void print(vector > ans)
{
    for (int i = 0; i < ans.size();
         i++) {
 
        for (int j = 0; j < 2; j++)
            cout << ans[i][j] << " ";
 
        cout << "\n";
    }
}
 
// Driver Code
int main()
{
    vector king = { 2, 3 };
 
    vector > queens
        = { { 0, 1 }, { 1, 0 },
            { 4, 0 }, { 0, 4 },
            { 3, 3 }, { 2, 4 } };
 
    vector > ans
        = findQueens(queens, king);
 
    print(ans);
}


Java
// Java program to implement
// the above approach
import java.io.*;
import java.util.*;
import java.util.stream.Collectors;
 
class GFG{
 
// Method to find the queen closest
// to king in an attacking position
private static int dis(int[] ans, int[] attacker)
{
    return Math.abs(ans[0] - attacker[0]) +
           Math.abs(ans[1] - attacker[1]);
}
 
// Method to find all the queens
// attacking the king in the chessboard
private static List> findQueens(
    int[][] queens, int[] king)
{
    List> sol = new ArrayList>();
    int[][] attackers = new int[8][2];
 
    for(int i = 0; i < 8; i++)
    {
        Arrays.fill(attackers[i], -1);
    }
 
    for(int i = 0; i < queens.length; i++)
    {
         
        // If king is horizontally on
        // the right of current queen
        if (king[0] == queens[i][0] &&
            king[1] > queens[i][1])
        {
             
            // If no attacker is present
            // in that direction
            if ((attackers[3][0] == -1) ||
 
                // Or if the current queen is
                // closest in that direction
                (dis(attackers[3], king) >
                    dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[3] = queens[i];
        }
 
        // If king is horizontally on
        // the left of current queen
        if (king[0] == queens[i][0] &&
            king[1] < queens[i][1])
        {
             
            // If no attacker is present
            // in that direction
            if ((attackers[4][0] == -1) ||
 
                // Or if the current queen is
                // closest in that direction
                (dis(attackers[4], king) >
                    dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[4] = queens[i];
        }
 
        // If the king is attacked by a
        // queen from the left by a queen
        // diagonal above
        if (king[0] - queens[i][0] ==
            king[1] - queens[i][1] &&
            king[0] > queens[i][0])
        {
             
            // If no attacker is present in
            // that direction
            if ((attackers[0][0] == -1) ||
 
                // Or the current queen is
                // the closest attacker in
                // that direction
                (dis(attackers[0], king) >
                    dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[0] = queens[i];
        }
 
        // If the king is attacked by a
        // queen from the left by a queen
        // diagonally below
        if (king[0] - queens[i][0] ==
            king[1] - queens[i][1] &&
            king[0] < queens[i][0])
        {
             
            // If no attacker is present in
            // that direction
            if ((attackers[7][0] == -1) ||
 
                // Or the current queen is
                // the closest attacker in
                // that direction
               (dis(attackers[7], king) >
                   dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[7] = queens[i];
        }
 
        // If the king is attacked by a
        // queen from the right by a queen
        // diagonally above
        if (king[1] - queens[i][1] == 0 &&
            king[0] > queens[i][0])
        {
             
            // If no attacker is present in
            // that direction
            if ((attackers[1][0] == -1) ||
 
                // Or the current queen is
                // the closest attacker in
                // that direction
                (dis(attackers[1], king) >
                    dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[1] = queens[i];
        }
 
        // If the king is attacked by a
        // queen from the right by a queen
        // diagonally below
        if (king[1] - queens[i][1] == 0 &&
            king[0] < queens[i][0])
        {
             
            // If no attacker is present in
            // that direction
            if ((attackers[6][0] == -1) ||
 
                // Or the current queen is
                // the closest attacker in
                // that direction
                (dis(attackers[6], king) >
                    dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[6] = queens[i];
        }
 
        // If a king is vertically below
        // the current queen
        if (king[0] - queens[i][0] ==
          -(king[1] - queens[i][1]) &&
            king[0] > queens[i][0])
        {
             
            // If no attacker is present in
            // that direction
            if ((attackers[2][0] == -1) ||
 
                // Or the current queen is
                // the closest attacker in
                // that direction
                (dis(attackers[2], king) >
                    dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[2] = queens[i];
        }
 
        // If a king is vertically above
        // the current queen
        if (king[0] - queens[i][0] ==
          -(king[1] - queens[i][1]) &&
            king[0] < queens[i][0])
        {
             
            // If no attacker is present in
            // that direction
            if ((attackers[5][0] == -1) ||
 
                // Or the current queen is
                // the closest attacker in
                // that direction
                (dis(attackers[5], king) >
                    dis(queens[i], king)))
 
                // Set current queen as
                // the attacker
                attackers[5] = queens[i];
        }
    }
 
    for(int i = 0; i < 8; i++)
        if (attackers[i][0] != -1)
            sol.add(
                Arrays.stream(
                    attackers[i]).boxed().collect(
                        Collectors.toList()));
 
    // Return the coordinates
    return sol;
}
 
// Print all the coordinates of the
// queens attacking the king
private static void print(List> ans)
{
    for(int i = 0; i < ans.size(); i++)
    {
        for(int j = 0; j < 2; j++)
            System.out.print(ans.get(i).get(j) + " ");
 
        System.out.println();
    }
}
 
// Driver Code
public static void main(String[] args)
{
    int[] king = { 2, 3 };
 
    int[][] queens = { { 0, 1 }, { 1, 0 },
                       { 4, 0 }, { 0, 4 },
                       { 3, 3 }, { 2, 4 } };
 
    List> ans = findQueens(queens, king);
 
    print(ans);
}
}
 
// This code is contributed by jithin


Python3
# Python3 program to implement
# the above approach
 
# Function to find the queen
# closest to king in an
# attacking position
def dis(ans, attacker):
 
    return (abs(ans[0] - attacker[0]) +
            abs(ans[1] - attacker[1]))
 
# Function to find all the
# queens attacking the king
# in the chessboard
def findQueens(queens, king):
 
    sol = []
    attackers = [[0 for x in range(8)]
                    for y in range(8)]
 
    # Iterating over the coordinates
    # of the queens
    for i in range(len(queens)):
 
        # If king is horizontally on
        # the right of current queen
        if (king[0] == queens[i][0] and
            king[1] > queens[i][1]):
 
            # If no attacker is present
            # in that direction
            if ((len(attackers[3]) == 0)
                 
                # Or if the current queen is
                # closest in that direction
                or ((dis(attackers[3], king) >
                     dis(queens[i], king)))):               
 
                # Set current queen as
                # the attacker
                attackers[3] = queens[i];
 
        # If king is horizontally on
        # the left of current queen
        if (king[0] == queens[i][0] and
            king[1] < queens[i][1]):
 
            # If no attacker is present
            # in that direction
            if ((len(attackers[4]) == 0)
 
                # Or if the current queen is
                # closest in that direction
                or (dis(attackers[4], king) >
                    dis(queens[i], king))):
 
                # Set current queen as
                # the attacker
                attackers[4] = queens[i];
 
        # If the king is attacked by a
        # queen from the left by a queen
        # diagonal above
        if (king[0] - queens[i][0] ==
            king[1] - queens[i][1] and
            king[0] > queens[i][0]):
 
            # If no attacker is present in
            # that direction
            if ((len(attackers[0]) == 0)
 
                # Or the current queen is
                # the closest attacker in
                # that direction
                or (dis(attackers[0], king) >
                    dis(queens[i], king))):
 
                # Set current queen as
                # the attacker
                attackers[0] = queens[i]
 
        # If the king is attacked by a
        # queen from the left by a queen
        # diagonally below
        if (king[0] - queens[i][0] ==
            king[1] - queens[i][1] and
            king[0] < queens[i][0]):
 
            # If no attacker is present in
            # that direction
            if ((len(attackers[7]) == 0)
 
                # Or the current queen is
                # the closest attacker in
                # that direction
                or (dis(attackers[7], king) >
                    dis(queens[i], king))):
 
                # Set current queen as
                # the attacker
                attackers[7] = queens[i]
 
        # If the king is attacked by a
        # queen from the right by a queen
        # diagonally above
        if (king[1] - queens[i][1] == 0 and
            king[0] > queens[i][0]):
 
            # If no attacker is present in
            # that direction
            if ((len(attackers[1]) == 0)
 
                # Or the current queen is
                # the closest attacker in
                # that direction
                or (dis(attackers[1], king) >
                    dis(queens[i], king))):
 
                # Set current queen as
                # the attacker
                attackers[1] = queens[i]
 
        # If the king is attacked by a
        # queen from the right by a queen
        # diagonally below
        if (king[1] - queens[i][1] == 0 and
            king[0] < queens[i][0]):
 
            # If no attacker is present in
            # that direction
            if ((len(attackers[6]) == 0)
 
                # Or the current queen is
                # the closest attacker in
                # that direction
                or (dis(attackers[6], king) >
                    dis(queens[i], king))):
 
                # Set current queen as
                # the attacker
                attackers[6] = queens[i];
 
        # If a king is vertically below
        # the current queen
        if (king[0] - queens[i][0] ==
            -(king[1] - queens[i][1]) and
            king[0] > queens[i][0]):
 
            # If no attacker is present in
            # that direction
            if ((len(attackers[2]) == 0)
 
                # Or the current queen is
                # the closest attacker in
                # that direction
                or (dis(attackers[2], king) >
                    dis(queens[i], king))):
 
                # Set current queen as
                # the attacker
                attackers[2] = queens[i]
 
        # If a king is vertically above
        # the current queen
        if (king[0] - queens[i][0] ==
          -(king[1] - queens[i][1]) and
            king[0] < queens[i][0]):
 
            # If no attacker is present in
            # that direction
            if ((len(attackers[5]) == 0)
 
                # Or the current queen is
                # the closest attacker in
                # that direction
                or (dis(attackers[5], king) >
                    dis(queens[i], king))):
 
                # Set current queen as
                # the attacker
                attackers[5] = queens[i]
                     
    for i in range(8):
        f = 1
        for x in attackers[i]:
          if x != 0:
            f = 0
            break
        if f == 0:
          sol.append(attackers[i])
 
    # Return the coordinates
    return sol
 
# Print all the coordinates of the
# queens attacking the king
def print_board(ans):
 
    for i in range(len(ans)):
        for j in range(2):
            print(ans[i][j],
                  end = " ")
             
        print()
 
# Driver Code
if __name__ == "__main__":
 
    king = [2, 3]
    queens = [[0, 1], [1, 0],
              [4, 0], [0, 4],
              [3, 3], [2, 4]]
    ans = findQueens(queens, king);
    print_board(ans);
 
# This code is contributed by Chitranayal


输出:
0 1 
2 4 
3 3

















时间复杂度: O(N),其中N是皇后数
辅助空间: O(N)