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

#include <bits/stdc++.h>
using namespace std;

const int N = 10;

void solve(){

    int a[N];

    int n;

    cin >> n;

    int flag = 1;  //记录打开的门的数量

    for(int i = 1; i <= 3; i++) cin >> a[i];

    for(int i = n; a[i] != 0; i = a[i]) flag++; 

    if(flag == 3) cout << "YES" << "\n";
    else cout << "NO" << "\n";

}

int main(){

    int _;

    cin >> _;

    while(_--){
        solve();
    }

    return 0;

}

#include <bits/stdc++.h>
using namespace std;

#define int long long

const int N = 1e6 + 10;

int a[N];

int b[N],c[N];

void solve(){

    int n, m;

    cin >> n >> m;

    for(int i = 1 ; i <= n ; i++){

        cin >> a[i];

        if(a[i] < a[i-1]){
            b[i] = a[i-1] - a[i];  //处理前缀   
        }
        else if(a[i] > a[i-1]){
            c[i] = a[i] - a[i-1];   //处理后缀
        }

        b[i] += b[i-1];  //构造前缀和数组
        c[i] += c[i-1];  //构造后缀和数组

    }   

    while(m--){

        int l, r;

        cin >> l >> r;

        if(l < r){
            cout << b[r] - b[l] << "\n";
        }
        else cout << c[l] - c[r] << "\n";

    }

}

signed main(){

    solve();

    return 0;

}

#include <bits/stdc++.h>
using namespace std;

void solve(){

    string s;

    cin >> s;

    int dep = 0, vis = 0;

    for(int i = 0 ; i < s.size() ; i++){

        if(s[i] == '(') dep++;
        else if(s[i] == ')'){dep--;
            if(dep < 0){
                if(vis > 0)dep++, vis--;
                else{  //vis <= 0 说明无法匹配，序列非法
                    dep = 1, vis = 0;
                    break;
                }
            }
        }
        else vis++;

        if(dep == 0 && vis == 1) dep++, vis--; 

    }

    if(abs(dep) == vis) cout << "YES" << '\n';
    else cout << "NO" << '\n';

}

int main(){

    int _;

    cin >> _;

    while(_--){
        solve();
    }

    return 0;

}