Java-递归

import java.util.*;
public class Solution {
    // 计算以root为根的树中路径和为sum的路径总数
    public int FindPath(TreeNode root, int sum) {
        // write code here
        if (root == null) {
            return 0;
        }
        int startAtRoot = Find(root, sum, 0);
        int l = FindPath(root.left, sum);
        int r = FindPath(root.right, sum);
        return l + r + startAtRoot;
    }
    // 计算以root为起点，到其某个子节点的路径和为sum的路径数
    public int Find(TreeNode root, int sum, int temp) {
        if (root == null) {
            return 0;
        }
        int count = 0;
        if (sum == temp + root.val) {
            count = 1;
        }
        temp += root.val;
        int l = Find(root.left, sum, temp);
        int r = Find(root.right, sum, temp);
        return l + r + count;
    }
}