day50（12.31）——leetcode面试经典150

112. 路径总和

112. 路径总和

dfs拿下

题目：

题解：

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public boolean flag = false;
    public void dfs(TreeNode node, int sum, int targetSum) {
        if(flag == true) {
            return;
        }
        if(node.left == null && node.right == null) {
            if(sum == targetSum) flag = true;
            return;
        }
        if(node.left != null)
        dfs(node.left, sum+node.left.val, targetSum);
        if(node.right != null)
        dfs(node.right, sum+node.right.val, targetSum);
    }

    public boolean hasPathSum(TreeNode root, int targetSum) {
        if(root == null) return false;
        dfs(root,root.val,targetSum);
        return flag;
    }
}