给定一个在每个节点上具有正值的二叉树，任务是打印通过在每个级别排列节点可以形成的最大数字。
例子：
Input: 4
/ \
2 59
/ \ / \
1 3 2 6
Output:
Maximum number at 0'th level is 4
Maximum number at 1'st level is 592
Maximum number at 2'nd level is 6321
Input: 1
/ \
2 3
/ \ \
4 5 8
/ \
6 79
Output:
Explanation :
The maximum number at the 0'th level is 1
The maximum number at 1'st level is 32
The maximum number at 2'nd level is 854
The maximum number at 3'rd level is 796方法：
- 使用 Level Order Traversal 一一遍历每一层的所有节点。
- 将它们的值存储在一个字符串向量中。
- 使用比较方法对向量进行排序以生成可能的最大数。
- 显示数字并为所有级别重复该过程。
下面的代码是上述方法的实现：
C++
// C++ program to find maximum number
// possible from nodes at each level.
#include
using namespace std;
/* A binary tree node representation */
struct Node {
int data;
struct Node *left, *right;
};
int myCompare(string X, string Y)
{
// first append Y at the end of X
string XY = X.append(Y);
// then append X at the end of Y
string YX = Y.append(X);
// Now see which of the two formed numbers is greater
return XY.compare(YX) > 0 ? 1 : 0;
}
// Function to print the largest value
// from the vector of strings
void printLargest(vector arr)
{
// Sort the numbers using comparison function
// myCompare() to compare two strings.
// Refer http:// www.cplusplus.com/reference/algorithm/sort/
sort(arr.begin(), arr.end(), myCompare);
for (int i = 0; i < arr.size(); i++)
cout << arr[i];
cout << "\n";
}
// Function to return the maximum number
// possible from nodes at each level
// using level order traversal
int maxLevelNumber(struct Node* root)
{
// Base case
if (root == NULL)
return 0;
// Initialize result
int result = root->data;
// Level Order Traversal
queue q;
q.push(root);
while (!q.empty()) {
// Get the size of the queue for the level
int count = q.size();
vector v;
// Iterate over all the nodes
while (count--) {
// Dequeue nodes from queue
Node* temp = q.front();
q.pop();
// push that node to vector
v.push_back(to_string(temp->data));
// Push left and right nodes to queue
// if present
if (temp->left != NULL)
q.push(temp->left);
if (temp->right != NULL)
q.push(temp->right);
}
// Print the maximum number at that level
printLargest(v);
}
return result;
}
/* Helper function that allocates a new node with the
given data and NULL left and right pointers. */
struct Node* newNode(int data)
{
struct Node* node = new Node;
node->data = data;
node->left = node->right = NULL;
return (node);
}
// Driver code
int main()
{
struct Node* root = newNode(1);
root->left = newNode(2);
root->right = newNode(3);
root->left->left = newNode(4);
root->left->right = newNode(5);
root->right->right = newNode(8);
root->right->right->left = newNode(6);
root->right->right->right = newNode(7);
/* Constructed Binary tree is:
1
/ \
2 3
/ \ \
4 5 8
/ \
6 7 */
maxLevelNumber(root);
return 0;
} Java
// Java program to find maximum number
// possible from nodes at each level
import java.util.*;
import java.lang.*;
import java.io.*;
class GFG{
// Node structure
static class node
{
int data;
node left = null;
node right = null;
}
// Creates and initialize a new node
static node newNode(int ch)
{
// Allocating memory to a new node
node n = new node();
n.data = ch;
n.left = null;
n.right = null;
return n;
}
// Function to print the largest value
// from the vector of strings
static void printLargest(ArrayList arr)
{
// Sort the numbers using comparison function
// myCompare() to compare two strings.
// Refer http:// www.cplusplus.com/reference/algorithm/sort/
Collections.sort(arr,new Comparator<>()
{
public int compare(String X, String Y)
{
// First append Y at the end of X
String XY = X + Y;
// Then append X at the end of Y
String YX = Y + X;
// Now see which of the two
// formed numbers is greater
return XY.compareTo(YX) > 0 ? -1 : 1;
}
});
for(int i = 0; i < arr.size(); i++)
System.out.print(arr.get(i));
System.out.println();
}
// Function to return the maximum number
// possible from nodes at each level
// using level order traversal
static int maxLevelNumber(node root)
{
// Base case
if (root == null)
return 0;
// Initialize result
int result = root.data;
// Level Order Traversal
Queue q = new LinkedList<>();
q.add(root);
while (!q.isEmpty())
{
// Get the size of the queue
// for the level
int count = q.size();
ArrayList v = new ArrayList<>();
// Iterate over all the nodes
while (count-->0)
{
// Dequeue nodes from queue
node temp = q.peek();
q.poll();
// push that node to vector
v.add(Integer.toString(temp.data));
// Push left and right nodes to queue
// if present
if (temp.left != null)
q.add(temp.left);
if (temp.right != null)
q.add(temp.right);
}
// Print the maximum number at that level
printLargest(v);
}
return result;
}
// Driver code
public static void main (String[] args)
{
node root = newNode(1);
root.left = newNode(2);
root.right = newNode(3);
root.left.left = newNode(4);
root.left.right = newNode(5);
root.right.right = newNode(8);
root.right.right.left = newNode(6);
root.right.right.right = newNode(7);
/* Constructed Binary tree is:
1
/ \
2 3
/ \ \
4 5 8
/ \
6 7 */
maxLevelNumber(root);
}
}
// This code is contributed by offbeat 输出：
1
32
854
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