feat: add 112

Author: Blankj

README.md

@@ -35,6 +35,7 @@
 |108|[Convert Sorted Array to Binary Search Tree][108]|Tree, Depth-first Search|
 |110|[Balanced Binary Tree][110]|Tree, Depth-first Search|
 |111|[Minimum Depth of Binary Tree][111]|Tree, Depth-first Search, Breadth-first Search|
+|112|[Path Sum][112]|Tree, Depth-first Search|
 
 
 ## Medium
@@ -85,6 +86,7 @@
 [108]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/108/README.md
 [110]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/110/README.md
 [111]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/111/README.md
+[112]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/112/README.md
 
 [008]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/008/README.md
 [019]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/019/README.md

note/112/README.md

@@ -0,0 +1,59 @@
+# [Path Sum][title]
+
+## Description
+
+Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.
+
+For example:
+
+Given the below binary tree and `sum = 22`,
+
+```
+ 5
+ / \
+ 4 8
+ / / \
+ 11 13 4
+ / \ \
+ 7 2 1
+
+```
+
+return true, as there exist a root-to-leaf path `5->4->11->2` which sum is 22.
+
+**Tags:** Tree, Depth-first Search
+
+
+## 思路
+
+题意是查找二叉树中是否存在从根结点到叶子的路径和为某一值，利用深搜在遇到叶子节点时判断是否满足即可。
+
+
+``` java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ * int val;
+ * TreeNode left;
+ * TreeNode right;
+ * TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+ public boolean hasPathSum(TreeNode root, int sum) {
+ if (root == null) return false;
+ if (root.left == null && root.right == null) return sum == root.val;
+ return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val);
+ }
+}
+```
+
+
+## 结语
+
+如果你同我一样热爱数据结构、算法、LeetCode，可以关注我GitHub上的LeetCode题解：[awesome-java-leetcode][ajl]
+
+
+
+[title]: https://leetcode.com/problems/path-sum
+[ajl]: https://github.com/Blankj/awesome-java-leetcode

project/leetcode/.idea/workspace.xml

@@ -0,0 +1,27 @@
+package com.blankj.easy._112;
+
+
+import com.blankj.structure.TreeNode;
+
+/**
+ * <pre>
+ * author: Blankj
+ * blog : http://blankj.com
+ * time : 2017/10/09
+ * desc :
+ * </pre>
+ */
+public class Solution {
+ public boolean hasPathSum(TreeNode root, int sum) {
+ if (root == null) return false;
+ if (root.left == null && root.right == null) return sum == root.val;
+ return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val);
+ }
+
+ public static void main(String[] args) {
+ Solution solution = new Solution();
+ TreeNode testData = TreeNode.createTestData("[5,4,8,11,null,13,4,7,2,null,null,null,1]");
+ TreeNode.print(testData);
+ System.out.println(solution.hasPathSum(testData, 22));
+ }
+}