finish "113. Path Sum II". Fix #113

Author: diguage

README.adoc

@@ -682,11 +682,11 @@
 |{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]
-//|{doc_base_url}/0113-path-sum-ii.adoc[Note]
-//|Medium
+|113
+|{leetcode_base_url}/path-sum-ii/[Path Sum II]
+|{source_base_url}/_0113_PathSumII.java[Java]
+|{doc_base_url}/0113-path-sum-ii.adoc[Note]
+|Medium
 
 |114
 |{leetcode_base_url}/flatten-binary-tree-to-linked-list/[Flatten Binary Tree to Linked List]

docs/0113-path-sum-ii.adoc

@@ -31,3 +31,12 @@ Return:
 ]
 ----
 
+=== 解题分析
+
+利用回溯+深度优先搜索即可解决。
+
+这样要重点注意的是：回溯时，前进和后退要成对出现。
+
+=== 参考资料
+
+. https://leetcode-cn.com/problems/path-sum-ii/solution/dfs-by-powcai-2/[DFS - 路径总和 II - 力扣（LeetCode）]

src/main/java/com/diguage/algorithm/leetcode/_0113_PathSumII.java

@@ -0,0 +1,49 @@
+package com.diguage.algorithm.leetcode;
+
+import com.diguage.algorithm.util.TreeNode;
+
+import java.util.*;
+
+import static com.diguage.algorithm.util.TreeNodeUtils.buildTree;
+import static java.util.Arrays.asList;
+
+/**
+ * = 113. Path Sum II
+ *
+ * https://leetcode.com/problems/path-sum-ii/[Path Sum II - LeetCode]
+ *
+ * @author D瓜哥, https://www.diguage.com/
+ * @since 2020-02-07 22:31
+ */
+public class _0113_PathSumII {
+
+    /**
+     * Runtime: 1 ms, faster than 100.00% of Java online submissions for Path Sum II.
+     * Memory Usage: 41.8 MB, less than 6.06% of Java online submissions for Path Sum II.
+     */
+    public List<List<Integer>> pathSum(TreeNode root, int sum) {
+        List<List<Integer>> result = new LinkedList<>();
+        dfs(root, sum, result, new ArrayDeque<>());
+        return result;
+    }
+
+    private void dfs(TreeNode root, int sum, List<List<Integer>> result, Deque<Integer> current) {
+        if (Objects.isNull(root)) {
+            return;
+        }
+        sum -= root.val;
+        current.addLast(root.val);
+        if (sum == 0 && Objects.isNull(root.left) && Objects.isNull(root.right)) {
+            result.add(new ArrayList<>(current));
+        }
+        dfs(root.left, sum, result, current);
+        dfs(root.right, sum, result, current);
+        current.removeLast();
+    }
+
+    public static void main(String[] args) {
+        _0113_PathSumII solution = new _0113_PathSumII();
+        List<List<Integer>> r1 = solution.pathSum(buildTree(asList(5, 4, 8, 11, null, 13, 4, 7, 2, null, null, null, null, 5, 1)), 22);
+        System.out.println(r1);
+    }
+}