Remove Invalid Parentheses in C++

Suppose we have a string of parentheses. We have to remove minimum number of invalid parentheses and return the well formed parentheses strings, So if the input is like “()(()()”, so the result will be [“()()()”, “()(())”]
To solve this, we will follow these steps −
Define a method called solve(), this will take pos, left, right, l, r, string array res and string temp.
Define a method called solve(), this will take pos, left, right, l, r, string array res and string temp.
if pos is same as size of s, then,if left is same as 0 and right is same as 0, then,if (m[temp] is non-zero) is false, then,insert temp at the end of resm[temp] := 1return
if pos is same as size of s, then,
if left is same as 0 and right is same as 0, then,if (m[temp] is non-zero) is false, then,insert temp at the end of resm[temp] := 1
if left is same as 0 and right is same as 0, then,
if (m[temp] is non-zero) is false, then,insert temp at the end of res
if (m[temp] is non-zero) is false, then,
insert temp at the end of res
insert temp at the end of res
m[temp] := 1
m[temp] := 1
return
return
if s[pos] is same as '(' and right > 0, then,call solve(pos + 1, left, right - 1, l, r, res, temp + empty string)
if s[pos] is same as '(' and right > 0, then,
call solve(pos + 1, left, right - 1, l, r, res, temp + empty string)
call solve(pos + 1, left, right - 1, l, r, res, temp + empty string)
Otherwise when s[pos] is same as ')' and left > 0, then −call solve(pos + 1, left - 1, right, l, r, res, temp + empty string)
Otherwise when s[pos] is same as ')' and left > 0, then −
call solve(pos + 1, left - 1, right, l, r, res, temp + empty string)
call solve(pos + 1, left - 1, right, l, r, res, temp + empty string)
if s[pos] is same as '(', then,call solve(pos + 1, left, right, l + 1, r, res, temp + "(")
if s[pos] is same as '(', then,
call solve(pos + 1, left, right, l + 1, r, res, temp + "(")
call solve(pos + 1, left, right, l + 1, r, res, temp + "(")
Otherwise when s[pos] is same as ')' and l > r, then −call solve(pos + 1, left, right, l, r + 1, res, temp + ')')
Otherwise when s[pos] is same as ')' and l > r, then −
call solve(pos + 1, left, right, l, r + 1, res, temp + ')')
call solve(pos + 1, left, right, l, r + 1, res, temp + ')')
if s[pos] is not equal to '(' and s[pos] is not equal to ')', then,call solve(pos + 1, left, right, l, r, res, temp + s[pos])
if s[pos] is not equal to '(' and s[pos] is not equal to ')', then,
call solve(pos + 1, left, right, l, r, res, temp + s[pos])
call solve(pos + 1, left, right, l, r, res, temp + s[pos])
From the main method do the following −
From the main method do the following −
Make one array res
Make one array res
l := 0, r := 0
l := 0, r := 0
for initializing i := 0, when i< size of s, increase i by 1 do −if s[i] is same as '(', then,increase r by 1Otherwise when s[i] is same as ')', then −if r is non-zero, then, decrease r by 1increase else l by 1
for initializing i := 0, when i< size of s, increase i by 1 do −
if s[i] is same as '(', then,increase r by 1
if s[i] is same as '(', then,
increase r by 1
increase r by 1
Otherwise when s[i] is same as ')', then −if r is non-zero, then, decrease r by 1increase else l by 1
Otherwise when s[i] is same as ')', then −
if r is non-zero, then, decrease r by 1
if r is non-zero, then, decrease r by 1
increase else l by 1
increase else l by 1
Call the function solve(0,l,r,0,0,res)
Call the function solve(0,l,r,0,0,res)
return res
return res
Let us see the following implementation to get better understanding −
 Live Demo
#include <bits/stdc++.h>
using namespace std;
void print_vector(vector<auto> v){
   cout << "[";
   for(int i = 0; i<v.size(); i++){
      cout << v[i] << ", ";
   }
   cout << "]"<<endl;
}
class Solution {
   public:
   string s;
   map <string ,int> m;
   void solve(int pos, int left, int right,int l, int r, vector <string> &res, string temp=""){
      if(pos == s.size()){
         if(left==0 && right==0 && l==r){
            if(!m[temp])
               res.push_back(temp);
            m[temp] = 1;
         }
         return;
      }
      if(s[pos] =='(' && right>0 ){
         solve(pos+1,left,right-1,l,r,res,temp+"");
      } else if(s[pos] ==')' && left>0) {
         solve(pos+1,left-1,right,l,r,res,temp+"");
      }
      if(s[pos] =='(')solve(pos+1,left,right,l+1,r,res,temp+"(");
      else if(s[pos] == ')' && l>r)solve(pos+1,left,right,l,r+1,res,temp+')');
      if(s[pos]!='(' && s[pos]!=')')solve(pos+1,left,right,l,r,res,temp+s[pos]);
   }
   vector<string> removeInvalidParentheses(string s) {
      vector <string > res;
      int l = 0;
      int r=0;
      this->s = s;
      for(int i =0;i<s.size();i++){
         if(s[i] == '('){
            r++;
         } else if(s[i]==')') {
            if(r)r--;
            else l++;
         }
      }
      solve(0,l,r,0,0,res);
      return res;
   }
};
main(){
   Solution ob;
   print_vector(ob.removeInvalidParentheses("()(()()"));
}
“()(()()”
[()()(), ()(()), ]