add prob #100; iterative solution

Author: randomwalk10

100_Same_Tree.cpp

@@ -0,0 +1,81 @@
+/*
+Given two binary trees, write a function to check if they are the same or not.
+
+Two binary trees are considered the same if they are structurally identical and the nodes have the same value.
+
+Example 1:
+
+Input:     1         1
+          / \       / \
+         2   3     2   3
+
+        [1,2,3],   [1,2,3]
+
+Output: true
+Example 2:
+
+Input:     1         1
+          /           \
+         2             2
+
+        [1,2],     [1,null,2]
+
+Output: false
+Example 3:
+
+Input:     1         1
+          / \       / \
+         2   1     1   2
+
+        [1,2,1],   [1,1,2]
+
+Output: false
+
+来源：力扣（LeetCode）
+链接：https://leetcode-cn.com/problems/same-tree
+著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。
+*/
+
+#include <stack>
+using namespace std;
+
+struct TreeNode {
+    int val;
+    TreeNode *left;
+    TreeNode *right;
+    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+};
+
+class Solution {
+public:
+    bool isSameTree(TreeNode* p, TreeNode* q) {
+		if((NULL==p)&&(NULL==q)) return true;
+		else if(NULL==p) return false;
+		else if(NULL==q) return false;
+		stack<TreeNode*> s_p;
+		stack<TreeNode*> s_q;
+
+		s_p.push(p);
+		s_q.push(q);
+		while(!s_p.empty()){
+			TreeNode* tmp_p = s_p.top(); s_p.pop();
+			TreeNode* tmp_q = s_q.top(); s_q.pop();
+			// compare val
+			if(tmp_p->val!=tmp_q->val) return false;
+			// right
+			if((NULL!=tmp_p->right)&&(NULL!=tmp_q->right)){
+				s_p.push(tmp_p->right);
+				s_q.push(tmp_q->right);
+			}
+			else if((NULL!=tmp_p->right)||(NULL!=tmp_q->right)) return false;
+			// left
+			if((NULL!=tmp_p->left)&&(NULL!=tmp_q->left)){
+				s_p.push(tmp_p->left);
+				s_q.push(tmp_q->left);
+			}
+			else if((NULL!=tmp_p->left)||(NULL!=tmp_q->left)) return false;
+		}
+
+		return true;
+    }
+};