add prob #257(2nd); iterative solution

Author: randomwalk10

257_Binary_Tree_Paths_2nd.cpp

@@ -0,0 +1,87 @@
+/* iterative solution */
+
+#include <string>
+#include <vector>
+#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:
+		vector<string> binaryTreePaths(TreeNode* root) {
+			vector<string> res;
+			if(root==NULL) return res;
+			vector<int> nums;
+			stack<TreeNode*> s_parent;
+			stack<int> s_depth;
+			stack<bool> s_visited;
+
+			s_parent.push(root);
+			s_depth.push(1);
+			s_visited.push(false);
+			while(!s_parent.empty()){
+				TreeNode* tmp_node = s_parent.top(); s_parent.pop();
+				int tmp_depth = s_depth.top(); s_depth.pop();
+				bool tmp_visited = s_visited.top(); s_visited.pop();
+
+				if(tmp_visited){
+					while(tmp_depth<(int)nums.size()){
+						nums.pop_back();
+					}
+					if((tmp_node->left==NULL)&&(tmp_node->right==NULL)){
+						string tmp_str;
+						for (int i = 0; i < (int)nums.size(); ++i) {
+							if(i>0) tmp_str.append("->");
+							int tmp_val = nums[i];
+							if(tmp_val<0){
+								tmp_val *= -1;
+								tmp_str.push_back('-');
+							}
+							else if(tmp_val==0){
+								tmp_str.push_back('0');
+								continue;
+							}
+
+							stack<char> s_char;
+							while(tmp_val>0){
+								s_char.push((tmp_val%10)+'0');
+								tmp_val /= 10;
+							}
+							while(!s_char.empty()){
+								tmp_str.push_back(s_char.top());
+								s_char.pop();
+							}
+						}
+						res.push_back(tmp_str);
+					}
+				}
+				else{
+					//right
+					if(tmp_node->right){
+						s_parent.push(tmp_node->right);
+						s_depth.push(tmp_depth+1);
+						s_visited.push(false);
+					}
+					//parent
+					s_parent.push(tmp_node);
+					s_depth.push(tmp_depth);
+					s_visited.push(true);
+					nums.push_back(tmp_node->val);
+					//left
+					if(tmp_node->left){
+						s_parent.push(tmp_node->left);
+						s_depth.push(tmp_depth+1);
+						s_visited.push(false);
+					}
+				}
+			}
+
+			return res;
+		}
+};