Niuke.com brushing questions-whether there is a path to the specified node in the binary tree

Problem Description

Given a binary tree and a value sum, judge whether there is a path from the root node to the leaf node that the sum of the node values ​​is equal to the sum.

Enter description:
Enter a tree

Output description:
output whether there is a path to the specified sum

Example

Example 1

Enter
22

Output (path included: 5->4->11->2)
true

Solutions

analysis

1. Judge all paths recursively, as long as it contains return true, the relationship between different paths is ||.

method

1. Recursively determine whether the path of the specified sum is included

Code

// 思路1
public class Solution {
    
    
    public boolean hasPathSum (TreeNode root, int sum) {
    
    
        // write code here
        if (root == null) {
    
    
            return false;
        }
        if (root.left == null && root.right == null) {
    
    
            return (sum - root.val == 0);
        }
        return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val);
    }
}

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Does the binary tree have the path of the specified node?