从三个不同的数组中找到三个元素，使得 a + b + c = sum

给定三个整数数组和一个“sum”，任务是检查是否有三个元素 a、b、c 使得 a + b + c = sum 并且 a、b 和 c 属于三个不同的数组。

例子 ：

Input : a1[] = { 1 , 2 , 3 , 4 , 5 };
    a2[] = { 2 , 3 , 6 , 1 , 2 };
    a3[] = { 3 , 2 , 4 , 5 , 6 };  
        sum = 9
Output : Yes
1  + 2  + 6 = 9  here 1 from a1[] and 2 from
a2[] and 6 from a3[]   
    
Input : a1[] = { 1 , 2 , 3 , 4 , 5 };
    a2[] = { 2 , 3 , 6 , 1 , 2 };
    a3[] = { 3 , 2 , 4 , 5 , 6 };   
         sum = 20 
Output : No 

一个天真的方法是运行三个循环并检查三个元素的总和，如果找到则打印存在，否则打印不存在。

C++

// C++ program to find three element
// from different three arrays such
// that a + b + c is equal to
// given sum
#include
using namespace std;
 
// Function to check if there is
// an element from each array such
// that sum of the three elements
// is equal to given sum.
bool findTriplet(int a1[], int a2[],
                 int a3[], int n1,
                 int n2, int n3, int sum)
{
    for (int i = 0; i < n1; i++)
    for (int j = 0; j < n2; j++)
        for (int k = 0; k < n3; k++)
            if (a1[i] + a2[j] + a3[k] == sum)
            return true;
 
    return false;
}
 
// Driver Code
int main()
{
    int a1[] = { 1 , 2 , 3 , 4 , 5 };
    int a2[] = { 2 , 3 , 6 , 1 , 2 };
    int a3[] = { 3 , 2 , 4 , 5 , 6 };
    int sum = 9;
    int n1 = sizeof(a1) / sizeof(a1[0]);
    int n2 = sizeof(a2) / sizeof(a2[0]);
    int n3 = sizeof(a3) / sizeof(a3[0]);
    findTriplet(a1, a2, a3, n1, n2, n3, sum)?
                cout << "Yes" : cout << "No";
    return 0;
}

Java

// Java program to find three element
// from different three arrays such
// that a + b + c is equal to
// given sum
class GFG
{
         
    // Function to check if there is
    // an element from each array such
    // that sum of the three elements
    // is equal to given sum.
    static boolean findTriplet(int a1[], int a2[],
                               int a3[], int n1,
                               int n2, int n3, int sum)
    {
        for (int i = 0; i < n1; i++)
            for (int j = 0; j < n2; j++)
                for (int k = 0; k < n3; k++)
                    if (a1[i] + a2[j] + a3[k] == sum)
                    return true;
     
        return false;
    }
     
    // Driver code
    public static void main (String[] args)
    {
        int a1[] = { 1 , 2 , 3 , 4 , 5 };
        int a2[] = { 2 , 3 , 6 , 1 , 2 };
        int a3[] = { 3 , 2 , 4 , 5 , 6 };
        int sum = 9;
         
        int n1 = a1.length;
        int n2 = a2.length;
        int n3 = a3.length;
         
        if(findTriplet(a1, a2, a3, n1, n2, n3, sum))
            System.out.print("Yes");
        else
            System.out.print("No");
    }
}
 
// This code is contributed by Anant Agarwal.

Python3

# Python3 program to find
# three element from different
# three arrays such that
# a + b + c is equal to
# given sum
 
# Function to check if there
# is an element from each
# array such that sum of the
# three elements is equal to
# given sum.
def findTriplet(a1, a2, a3,
                n1, n2, n3, sum):
 
    for i in range(0 , n1):
        for j in range(0 , n2):
            for k in range(0 , n3):
                if (a1[i] + a2[j] +
                    a3[k] == sum):
                    return True
 
    return False
 
# Driver Code
a1 = [ 1 , 2 , 3 , 4 , 5 ]
a2 = [ 2 , 3 , 6 , 1 , 2 ]
a3 = [ 3 , 2 , 4 , 5 , 6 ]
sum = 9
n1 = len(a1)
n2 = len(a2)
n3 = len(a3)
print("Yes") if findTriplet(a1, a2, a3,
                            n1, n2, n3,
                            sum) else print("No")
 
# This code is contributed
# by Smitha

C#

// C# program to find three element
// from different three arrays such
// that a + b + c is equal to
// given sum
using System;
 
public class GFG
{
 
// Function to check if there is an
// element from each array such that
// sum of the three elements is
// equal to given sum.
static bool findTriplet(int []a1, int []a2,
                        int []a3, int n1,
                        int n2, int n3,
                        int sum)
{
     
    for (int i = 0; i < n1; i++)
     
        for (int j = 0; j < n2; j++)
         
            for (int k = 0; k < n3; k++)
            if (a1[i] + a2[j] + a3[k] == sum)
            return true;
 
    return false;
}
 
    // Driver Code
    static public void Main ()
    {
        int []a1 = {1 , 2 , 3 , 4 , 5};
        int []a2 = {2 , 3 , 6 , 1 , 2};
        int []a3 = {3 , 2 , 4 , 5 , 6};
        int sum = 9;
        int n1 = a1.Length;
        int n2 = a2.Length;
        int n3 = a3.Length;
        if(findTriplet(a1, a2, a3, n1,
                       n2, n3, sum))
        Console.WriteLine("Yes");
        else
        Console.WriteLine("No");
    }
}
 
// This code is contributed by vt_m.

Javascript

 
// JavaScript program to find three element
// from different three arrays such
// that a + b + c is equal to
// given sum
 
// Function to check if there is
// an element from each array such
// that sum of the three elements
// is equal to given sum.
function findTriplet(a1, a2, a3, n1,
                      n2, n3, sum)
{
    for (var i = 0; i < n1; i++)
    for (var j = 0; j < n2; j++)
        for (var k = 0; k < n3; k++)
            if (a1[i] + a2[j] + a3[k] == sum)
            return true;
 
    return false;
}
 
// Driver Code
var a1 = [ 1 , 2 , 3 , 4 , 5 ];
var a2 = [ 2 , 3 , 6 , 1 , 2 ];
var a3 = [ 3 , 2 , 4 , 5 , 6 ];
var sum = 9;
var n1 = a1.length;
var n2 = a2.length;
var n3 = a3.length;
findTriplet(a1, a2, a3, n1, n2, n3, sum)?
            document.write("Yes") : document.write("No");
 
 

输出 ：

Yes

时间复杂度： O(n ³ )
空间复杂度： O(1)

一个有效的解决方案是将第一个数组的所有元素存储在哈希表中（在 C++ 中为 unordered_set），并一一计算数组最后两个元素的两个元素的总和，然后从给定的数字 k 中减去，如果它存在于哈希表中，则检查哈希表然后打印存在，否则不存在。

1. Store all elements of first array in hash table
2. Generate all pairs of elements from two arrays using
   nested loop. For every pair (a1[i], a2[j]), check if
   sum - (a1[i] + a2[j]) exists in hash table. If yes
   return true.      

下面是上述想法的实现。

C++

// C++ program to find three element
// from different three arrays such
// that a + b + c is equal to
// given sum
#include
using namespace std;
 
// Function to check if there is
// an element from each array such
// that sum of the three elements is
// equal to given sum.
bool findTriplet(int a1[], int a2[],
                 int a3[], int n1,
                 int n2, int n3,
                 int sum)
{
    // Store elements of
    // first array in hash
    unordered_set  s;
    for (int i = 0; i < n1; i++)
        s.insert(a1[i]);
 
    // sum last two arrays
    // element one by one
    for (int i = 0; i < n2; i++)
    {
        for (int j = 0; j < n3; j++)
        {
            // Consider current pair and
            // find if there is an element
            // in a1[] such that these three
            // form a required triplet
            if (s.find(sum - a2[i] - a3[j]) !=
                                       s.end())
                return true;
        }
    }
 
    return false;
}
 
// Driver Code
int main()
{
    int a1[] = { 1 , 2 , 3 , 4 , 5 };
    int a2[] = { 2 , 3 , 6 , 1 , 2 };
    int a3[] = { 3 , 2 , 4 , 5 , 6 };
    int sum = 9;
    int n1 = sizeof(a1) / sizeof(a1[0]);
    int n2 = sizeof(a2) / sizeof(a2[0]);
    int n3 = sizeof(a3) / sizeof(a3[0]);
    findTriplet(a1, a2, a3, n1, n2, n3, sum)?
    cout << "Yes" : cout << "No";
 
    return 0;
}

Java

// Java program to find three element
// from different three arrays such
// that a + b + c is equal to
// given sum
import java.util.*;
 
class GFG
{
 
    // Function to check if there is
    // an element from each array such
    // that sum of the three elements is
    // equal to given sum.
    static boolean findTriplet(int a1[], int a2[], int a3[],
                                int n1, int n2, int n3,
                                int sum)
    {
        // Store elements of
        // first array in hash
        HashSet s = new HashSet();
        for (int i = 0; i < n1; i++)
        {
            s.add(a1[i]);
        }
 
        // sum last two arrays
        // element one by one
        ArrayList al = new ArrayList<>(s);
        for (int i = 0; i < n2; i++)
        {
            for (int j = 0; j < n3; j++)
            {
                 
                // Consider current pair and
                // find if there is an element
                // in a1[] such that these three
                // form a required triplet
                if (al.contains(sum - a2[i] - a3[j]) &
                            al.indexOf(sum - a2[i] - a3[j])
                            != al.get(al.size() - 1))
                {
                    return true;
                }
            }
        }
        return false;
    }
 
    // Driver Code
    public static void main(String[] args)
    {
        int a1[] = {1, 2, 3, 4, 5};
        int a2[] = {2, 3, 6, 1, 2};
        int a3[] = {3, 2, 4, 5, 6};
        int sum = 9;
        int n1 = a1.length;
        int n2 = a2.length;
        int n3 = a3.length;
        if (findTriplet(a1, a2, a3, n1, n2, n3, sum))
        {
            System.out.println("Yes");
        }
        else
        {
            System.out.println("No");
        }
    }
}
 
// This code is contributed by 29AjayKumar

蟒蛇3

# Python3 program to find three element
# from different three arrays such
# that a + b + c is equal to
# given sum
 
# Function to check if there is
# an element from each array such
# that sum of the three elements is
# equal to given sum.
def findTriplet(a1, a2, a3,
                n1, n2, n3, sum):
 
    # Store elements of first
    # array in hash
    s = set()
 
    # sum last two arrays element
    # one by one
    for i in range(n1):
        s.add(a1[i])
 
    for i in range(n2):
        for j in range(n3):
 
            # Consider current pair and
            # find if there is an element
            # in a1[] such that these three
            # form a required triplet
            if sum - a2[i] - a3[j] in s:
                return True
    return False
 
# Driver code
a1 = [1, 2, 3, 4, 5]
a2 = [2, 3, 6, 1, 2]
a3 = [3, 24, 5, 6]
n1 = len(a1)
n2 = len(a2)
n3 = len(a3)
sum = 9
if findTriplet(a1, a2, a3,
               n1, n2, n3, sum) == True:
    print("Yes")
else:
    print("No")
 
# This code is contributed by Shrikant13

C＃

// C# program to find three element
// from different three arrays such
// that a + b + c is equal to
// given sum
using System;
using System.Collections.Generic;
 
class GFG
{
 
    // Function to check if there is
    // an element from each array such
    // that sum of the three elements is
    // equal to given sum.
    static bool findTriplet(int []a1, int []a2, int []a3,
                                int n1, int n2, int n3,
                                int sum)
    {
        // Store elements of
        // first array in hash
        HashSet s = new HashSet();
        for (int i = 0; i < n1; i++)
        {
            s.Add(a1[i]);
        }
 
        // sum last two arrays
        // element one by one
        List al = new List(s);
        for (int i = 0; i < n2; i++)
        {
            for (int j = 0; j < n3; j++)
            {
                 
                // Consider current pair and
                // find if there is an element
                // in a1[] such that these three
                // form a required triplet
                if (al.Contains(sum - a2[i] - a3[j]) &
                            al.IndexOf(sum - a2[i] - a3[j])
                            != al[al.Count - 1])
                {
                    return true;
                }
            }
        }
        return false;
    }
 
    // Driver Code
    public static void Main(String[] args)
    {
        int []a1 = {1, 2, 3, 4, 5};
        int []a2 = {2, 3, 6, 1, 2};
        int []a3 = {3, 2, 4, 5, 6};
        int sum = 9;
        int n1 = a1.Length;
        int n2 = a2.Length;
        int n3 = a3.Length;
        if (findTriplet(a1, a2, a3, n1, n2, n3, sum))
        {
            Console.WriteLine("Yes");
        }
        else
        {
            Console.WriteLine("No");
        }
    }
}
 
// This code is contributed by PrinciRaj1992

Javascript

  
// Javascript program to find three element
// from different three arrays such
// that a + b + c is equal to
// given sum
 
// Function to check if there is
// an element from each array such
// that sum of the three elements is
// equal to given sum.
function findTriplet(a1, a2, a3, n1, n2, n3, sum)
{
 
    // Store elements of
    // first array in hash
    var s = new Set();
    for (var i = 0; i < n1; i++)
        s.add(a1[i]);
 
    // sum last two arrays
    // element one by one
    for (var i = 0; i < n2; i++)
    {
        for (var j = 0; j < n3; j++)
        {
            // Consider current pair and
            // find if there is an element
            // in a1[] such that these three
            // form a required triplet
            if (s.has(sum - a2[i] - a3[j]))
                return true;
        }
    }
 
    return false;
}
 
// Driver Code
var a1 = [1 , 2 , 3 , 4 , 5];
var a2 = [2 , 3 , 6 , 1 , 2];
var a3 = [3 , 2 , 4 , 5 , 6];
var sum = 9;
var n1 = a1.length;
var n2 = a2.length;
var n3 = a3.length;
findTriplet(a1, a2, a3, n1, n2, n3, sum)?
document.write( "Yes" ): document.write( "No");
 
// This code is contributed by famously.

输出 ：

Yes

时间复杂度： O(n ² )
辅助空间： O(n)

参考 ：
http://stackoverflow.com/questions/2070359/finding-three-elements-in-an-array-whose-sum-is-closest-to-a-given-number

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