非常非常非常好！path-sum-iii

https://leetcode.com/problems/path-sum-iii/

最终我还是没做出好的解法。还是看的别人的解法。

即使看了别人的解法，开始还实现错了。

还有很长的路要走。

package com.company;

// https://discuss.leetcode.com/topic/64388/simple-ac-java-solution-dfs
// 比我的方法,好多了。唉。
// 我开始准备DFS,然后在栈里面遍历的,非常复杂。
// 唉,还是思维太局限了。
// 我的第一种解法,还实现错了。直接递归是造成和跳跃。。唉。。差劲

class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) {
        val = x;
    }
}

class Solution {

    public int pathSum(TreeNode root, int sum) {
        if (root == null) {
            return 0;
        }

        int ret = pathWithRoot(root, sum) + pathSum(root.left, sum) + pathSum(root.right, sum);
        return ret;
    }
    private int pathWithRoot(TreeNode root, int sum) {
        if (root == null) {
            return 0;
        }
        int ret = 0;
        if (root.val == sum) {
            ret++;
        }
        ret += pathWithRoot(root.left, sum-root.val) + pathWithRoot(root.right, sum-root.val);
        return ret;
    }
}

public class Main {

    public static void main(String[] args) {
        // write your code here
        System.out.println("Hello");
        Solution solution = new Solution();

        TreeNode root = new TreeNode(10);
        TreeNode root1 = new TreeNode(5);
        TreeNode root2 = new TreeNode(-3);
        TreeNode root3 = new TreeNode(3);
        TreeNode root4 = new TreeNode(2);
        TreeNode root5 = new TreeNode(11);
        TreeNode root6 = new TreeNode(3);
        TreeNode root7 = new TreeNode(-2);
        TreeNode root8 = new TreeNode(1);
        root.left = root1;
        root.right = root2;
        root1.left = root3;
        root1.right = root4;
        root2.right = root5;
        root3.left = root6;
        root3.right = root7;
        root4.right = root8;

        int ret = solution.pathSum(root, 8);
        System.out.printf("Result is %d\n", ret);

    }
}

下面是写错了的代码。。

package com.company;

// https://discuss.leetcode.com/topic/64388/simple-ac-java-solution-dfs
// 比我的方法,好多了。唉。
// 我开始准备DFS,然后在栈里面遍历的,非常复杂。
// 唉,还是思维太局限了。
// 我的第一种解法,还实现错了。直接递归是造成和跳跃。。唉。。差劲

class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) {
        val = x;
    }
}

class Solution {

    public int pathSum(TreeNode root, int sum) {
        if (root == null) {
            return 0;
        }
        int ret = 0;
        if (root.val == sum) {
            ret++;
        }
        ret += pathSum(root.left, sum)
                + pathSum(root.left, sum-root.val)
                + pathSum(root.right, sum)
                + pathSum(root.right, sum-root.val);
        System.out.printf("root %d, ret %d, sum %d\n", root.val, ret, sum);
        return ret;
    }
}

public class Main {

    public static void main(String[] args) {
        // write your code here
        System.out.println("Hello");
        Solution solution = new Solution();

        TreeNode root = new TreeNode(10);
        TreeNode root1 = new TreeNode(5);
        TreeNode root2 = new TreeNode(-3);
        TreeNode root3 = new TreeNode(3);
        TreeNode root4 = new TreeNode(2);
        TreeNode root5 = new TreeNode(11);
        TreeNode root6 = new TreeNode(3);
        TreeNode root7 = new TreeNode(-2);
        TreeNode root8 = new TreeNode(1);
        root.left = root1;
        root.right = root2;
        root1.left = root3;
        root1.right = root4;
        root2.right = root5;
        root3.left = root6;
        root3.right = root7;
        root4.right = root8;

        int ret = solution.pathSum(root, 8);
        System.out.printf("Result is %d\n", ret);

    }
}