finish "112. Path Sum". Fix #112

Author: diguage

README.adoc

@@ -676,12 +676,12 @@
 |{doc_base_url}/0111-minimum-depth-of-binary-tree.adoc[Note]
 |Easy
 
-//|112
-//|{leetcode_base_url}/path-sum/[Path Sum]
-//|{source_base_url}/_0112_PathSum.java[Java]
-//|{doc_base_url}/0112-path-sum.adoc[Note]
-//|Easy
-//
+|112
+|{leetcode_base_url}/path-sum/[Path Sum]
+|{source_base_url}/_0112_PathSum.java[Java]
+|{doc_base_url}/0112-path-sum.adoc[Note]
+|Easy
+
 //|113
 //|{leetcode_base_url}/path-sum-ii/[Path Sum II]
 //|{source_base_url}/_0113_PathSumII.java[Java]

docs/0112-path-sum.adoc

@@ -23,3 +23,6 @@ Given the below binary tree and `sum = 22`,
 
 return true, as there exist a root-to-leaf path `5->4->11->2` which sum is 22.
 
+=== 解题分析
+
+减去当前节点值的只，然后递归调用，到叶子节点和目标值相等即可。

src/main/java/com/diguage/algorithm/leetcode/_0112_PathSum.java

@@ -0,0 +1,50 @@
+package com.diguage.algorithm.leetcode;
+
+import com.diguage.algorithm.util.TreeNode;
+
+import java.util.Objects;
+
+import static com.diguage.algorithm.util.TreeNodeUtils.*;
+import static java.util.Arrays.*;
+
+/**
+ * = 112. Path Sum
+ *
+ * https://leetcode.com/problems/path-sum/[Path Sum - LeetCode]
+ *
+ * @author D瓜哥, https://www.diguage.com/
+ * @since 2020-02-07 21:53
+ */
+public class _0112_PathSum {
+
+    /**
+     * Runtime: 0 ms, faster than 100.00% of Java online submissions for Path Sum.
+     * Memory Usage: 39.1 MB, less than 5.88% of Java online submissions for Path Sum.
+     */
+    public boolean hasPathSum(TreeNode root, int sum) {
+        if (Objects.isNull(root)) {
+            return false;
+        }
+        if (Objects.nonNull(root) && root.val == sum
+                && Objects.isNull(root.left) && Objects.isNull(root.right)) {
+            return true;
+        }
+        boolean result = false;
+        if (Objects.nonNull(root.left)) {
+            result = hasPathSum(root.left, sum - root.val);
+        }
+        if (result) {
+            return true;
+        }
+        if (Objects.nonNull(root.right)) {
+            result = hasPathSum(root.right, sum - root.val);
+        }
+        return result;
+    }
+
+    public static void main(String[] args) {
+        _0112_PathSum solution = new _0112_PathSum();
+        boolean r1 = solution.hasPathSum(buildTree(asList(5, 4, 8, 11, null, 13, 4, 7, 2, null, null, null, null, null, 1)), 22);
+        System.out.println(r1);
+    }
+}