Codeforces 1323C Unusual Competitions

题目链接

本题可以贪心，假设满足条件, 遍历串, 当'('的数量大于')'时, 接下来一定能够不交换合法, 如果')'数量大于'('时, 就一定需要交换顺序, 注意特判')('这种情况即可

#include<bits/stdc++.h>
using namespace std;
#define ms(x,y) memset(x, y, sizeof(x))
#define lowbit(x) ((x)&(-x))
typedef long long LL;
typedef pair<int,int> pii;

const int maxn = 1e6+7;
char str[maxn];


void run_case() {
    int n;
    cin >> n >> (str+1);
    int sum = 0, ans = 0;
    for(int i = 1; i <= n; ++i) {
        if(str[i] == '(') sum++;
        else sum--;
        if(sum < 0) ans++;
        if(sum == -1 && str[i] == ')') ans++;
    }
    if(sum) {
        cout << -1;
        return;
    }
    cout << ans;

}

int main() {
    ios::sync_with_stdio(false), cin.tie(0);
    cout.flags(ios::fixed);cout.precision(2);
    //int t; cin >> t;
    //while(t--)
    run_case();
    cout.flush();
    return 0;
}