Update 0112.路径总和.md

add java iteration method for leetcode 113 (DFS统一迭代法)

problems/0112.路径总和.md

@@ -446,6 +446,52 @@ class Solution {
     }
 }
 ```
+```java
+// 解法3 DFS统一迭代法
+class Solution {
+    public List<List<Integer>> pathSum(TreeNode root, int targetSum) {
+        List<List<Integer>> result = new ArrayList<>();
+        Stack<TreeNode> nodeStack = new Stack<>();
+        Stack<Integer> sumStack = new Stack<>();
+        Stack<ArrayList<Integer>> pathStack = new Stack<>();
+        if(root == null)
+            return result;
+        nodeStack.add(root);
+        sumStack.add(root.val);
+        pathStack.add(new ArrayList<>());
+
+        while(!nodeStack.isEmpty()){
+            TreeNode currNode = nodeStack.peek();
+            int currSum = sumStack.pop();
+            ArrayList<Integer> currPath = pathStack.pop();
+            if(currNode != null){
+                nodeStack.pop();
+                nodeStack.add(currNode);
+                nodeStack.add(null);
+                sumStack.add(currSum);
+                currPath.add(currNode.val);
+                pathStack.add(new ArrayList(currPath));
+                if(currNode.right != null){
+                    nodeStack.add(currNode.right);
+                    sumStack.add(currSum + currNode.right.val);
+                    pathStack.add(new ArrayList(currPath));
+                }
+                if(currNode.left != null){
+                    nodeStack.add(currNode.left);
+                    sumStack.add(currSum + currNode.left.val);
+                    pathStack.add(new ArrayList(currPath));
+                }
+            }else{
+                nodeStack.pop();
+                TreeNode temp = nodeStack.pop();
+                if(temp.left == null && temp.right == null && currSum == targetSum)
+                    result.add(new ArrayList(currPath));
+            }
+        }
+        return result;
+    }
+}
+```
 
 ## python