Educational Codeforces Round 132 (Rated for Div. 2) C

https://codeforces.com/contest/1709/problem/C

题意

给你一个只包含{(,),?}的字符串。问有没有可能通过把?变成(或者)，使得只存在唯一的改变方法能让字符串变为regular的
regular定义：A regular bracket sequence (or, shortly, an RBS) is a bracket sequence that can be transformed into a correct arithmetic expression by inserting characters "1" and "+" between the original characters of the sequence.

思路

本题思路为贪心。
regular串满足串任意长度的前缀中左括号的数量>=右括号的数量，可以用一个变量tot来记录左括号数量减去右括号的数量，同时记录问号的数量cnt
如果tot<0，那就让其中一个问号变成左括号，cnt--,tot++
最后yes的判断条件是cnt=0 or cnt=tot or len(s)=2

code

#include
#define ll long long
using namespace std;
const int N = 200005;
int t,n,q;
string s;
int pre[N][3];
int cnt[2],sum[N];

int main(){
    cin>>t;
    while(t--){
        cin>>s;
        n=s.length();
        if(n==2){
            puts("YES");
            continue;
        }
        int tot=0,quest=0;
        for(int i=0;i