Q112Path Sum.md

Q112Path Sum

Solution 1 Recursive

Idea:

Use recursive method to deal with each level.

Time Complexity:

O(n)

Space Complexity:

O(1)

Source code:

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public boolean hasPathSum(TreeNode root, int sum) {
        if(root==null) return false;
        if(root.left==null&&root.right==null&&sum==root.val) return true;
        return hasPathSum(root.left,sum-root.val)||hasPathSum(root.right,sum-root.val);

    }
}

Reference:

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