added cpp program to generate parenthesis issue #482

C++/2. Backtracking/generate-parenthesis.cpp

@@ -0,0 +1,37 @@
+/* Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
+* Input: n = 3
+* Output: ["((()))","(()())","(())()","()(())","()()()"]
+*/
+
+#include <iostream>
+#include <bits/stdc++.h>
+using namespace std;
+
+void backtrack(vector<string> &res,string curr,int open,int close,int max) {
+  if(curr.length()==max*2) { 
+    res.push_back(curr);
+    return;
+  }
+  else {
+    if(open<max)
+      backtrack(res,curr+"(",open+1,close,max);
+    if(close<open)
+      backtrack(res,curr+")",open,close+1,max);
+
+  }      
+}
+
+vector<string> generateParenthesis(int n) {
+  vector<string> res;
+  backtrack(res,"",0,0,n);
+  return res;
+}
+
+int main() {
+	int n = 3;
+	vector<string> parenthesis = generateParenthesis(n);
+  for(auto str : parenthesis) {
+    cout << str << " ";
+  }
+	return 0;
+}