题解 | #牛的奶量统计II#

使用深度遍历的思路，从上往下传上面的节点值，
并用递归进行调用




import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @param targetSum int整型 
     * @return bool布尔型
     */
    public boolean hasPathSumII (TreeNode root, int targetSum) {
        // write code here
        if (root == null) {
            return false;
        }
       return hasCurrentPathSumII(root, targetSum, root.val);
    }   

    public boolean hasCurrentPathSumII (TreeNode root, int targetSum, int parentSum) {
        // write code here
        
        if (root.left != null) {
            int currentSum = root.left.val + parentSum;
            if (currentSum == targetSum) {
                return true;
            }
            if (root.left.val == targetSum) {
                return true;
            }
            if (hasCurrentPathSumII(root.left, targetSum, currentSum)) {
                return true;
            }
            if (hasCurrentPathSumII(root.left, targetSum, 0)) {
                return true;
            }
        }

        if (root.right != null) {
             int currentSum = root.right.val + parentSum;
            if (currentSum == targetSum) {
                return true;
            }
            if (root.right.val == targetSum) {
                return true;
            }
            if (hasCurrentPathSumII(root.right, targetSum, currentSum)) {
                return true;
            }
            if (hasCurrentPathSumII(root.right, targetSum, 0)) {
                return true;
            }
        }
        return false;
    }   
}