remove_invalid_parentheses

Author: hitzzc

README.md

@@ -216,6 +216,7 @@ Golang solution for leetcode. For each problem, there is a simple *_test.go to t
 #### [297. Serialize and Deserialize Binary Tree](https://github.com/hitzzc/go-leetcode/tree/master/serialize_and_deserialize_binary_tree)
 #### [299. Bulls and Cows](https://github.com/hitzzc/go-leetcode/tree/master/bulls_and_cows)
 #### [300. Longest Increasing Subsequence](https://github.com/hitzzc/go-leetcode/tree/master/longest_increasing_subsequence)
+#### [301. Remove Invalid Parentheses](https://github.com/hitzzc/go-leetcode/tree/master/remove_invalid_parentheses)
 
 
 

remove_invalid_parentheses/remove_invalid_parentheses.cpp

@@ -0,0 +1,42 @@
+#include <string>
+#include <unordered_set>
+using namespace std;
+
+class Solution {
+public:
+    vector<string> removeInvalidParentheses(string s) {
+        int left = 0;
+        int right = 0;
+        for (auto ch: s) {
+        	if (ch == '(') ++left;
+        	if (ch == ')') {
+        		if (left > 0) --left;
+        		else ++right;
+        	}
+        }
+        vector<string> results;
+        unordered_set<string> unique;
+        DFS(s, 0, 0, left, right, "", results, unique);
+        return results;
+    }
+
+    void DFS(string&s, int idx, int pair, int left, int right, string solution, vector<string>& results, unordered_set<string>& unique) {
+    	if (idx == s.size()) {
+    		if (left == 0 && right == 0 && pair == 0 && unique.find(solution) == unique.end()) {
+    			results.push_back(solution);
+    			unique.insert(solution);
+    		}
+    		return;
+    	}
+    	if (s[idx] == '(') {
+    		if (left > 0) DFS(s, idx+1, pair, left-1, right, solution, results, unique);
+    		DFS(s, idx+1, pair+1, left, right, solution+"(", results, unique);
+    	}else if (s[idx] == ')') {
+    		if (right > 0) DFS(s, idx+1, pair, left, right-1, solution, results, unique);
+    		if (pair > 0) DFS(s, idx+1, pair-1, left, right, solution+")", results, unique);
+    	}else {
+    		DFS(s, idx+1, pair, left, right, solution+s[idx], results, unique);
+    	}
+    	return;
+    }
+};