Sum Root to Leaf Numbers

Change-Id: Ie6fe40e8e08055d24ea49326cb78257a40d76f4f

Author: applewjg

SumRoottoLeafNumbers.java

@@ -0,0 +1,77 @@
+/*
+ Author:     King, [email protected]
+ Date:       Jan 02, 2014
+ Problem:    Sum Root to Leaf Numbers
+ Difficulty: Easy
+ Source:     https://oj.leetcode.com/problems/sum-root-to-leaf-numbers/
+ Notes:
+ Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.
+ An example is the root-to-leaf path 1->2->3 which represents the number 123.
+ Find the total sum of all root-to-leaf numbers.
+ For example,
+   1
+  / \
+ 2   3
+ The root-to-leaf path 1->2 represents the number 12.
+ The root-to-leaf path 1->3 represents the number 13.
+ Return the sum = 12 + 13 = 25.
+
+ Solution: 1. Recursion (add to sum when reaching the leaf).
+           2. Iterative solution.
+ */
+
+/**
+ * Definition for binary tree
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    int sumNumbers(TreeNode *root) {
+        return sumNumbers_1(root);
+    }
+    
+    int sumNumbers_1(TreeNode *root) {
+        int sum = 0;
+        sumNumbersRe(root, 0, sum);
+        return sum;
+    }
+    
+    void sumNumbersRe(TreeNode *node, int num, int &sum) {
+        if (!node) return;
+        num = num * 10 + node->val;
+        if (!node->left && !node->right) { 
+            sum += num;
+            return;
+        }
+        sumNumbersRe(node->left, num, sum);
+        sumNumbersRe(node->right, num, sum);
+    }
+    
+    int sumNumbers_2(TreeNode *root) {
+        if (!root) return 0;
+        int res = 0;
+        queue<pair<TreeNode *, int>> q;
+        q.push(make_pair(root, 0));
+        while(!q.empty())
+        {
+            TreeNode *node = q.front().first;
+            int sum = q.front().second * 10 + node->val;
+            q.pop();
+            if (!node->left && !node->right)
+            {
+                res += sum;
+                continue;
+            }
+            if (node->left)
+                q.push(make_pair(node->left, sum));
+            if (node->right)
+                q.push(make_pair(node->right, sum));
+        }
+        return res;
+    }
+};