LOJ#6085. 「美团 CodeM 资格赛」优惠券(set)

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 1e6 + 10;
inline int read() {
    char c = getchar(); int x = 0, f = 1;
    while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}
    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
    return x * f;
}
int M, las[MAXN], op[MAXN];//las上一次进去的时间  op最后一次操作的位置 
set<int> ms;
signed main() {
    //freopen("a.in", "r", stdin);
    M = read();
    for(int i = 1; i <= M; i++) {
        char c = 'g';
        while(c != 'I' && c != 'O' && c != '?') c = getchar();
        if(c == 'I') {
            int x = read();
            if(las[x]) {//在里面 
                auto pos = ms.upper_bound(op[x]);
                if(pos == ms.end() || (*pos > i)) return printf("%d", i), 0;
                else ms.erase(pos);
            }
            las[x] = 1;
            op[x] = i;
        } else if(c == 'O') {
            int x = read();
            if(!las[x]) {
                auto pos = ms.upper_bound(op[x]);
                if(pos == ms.end() || (*pos > i)) return printf("%d", i), 0;
                else ms.erase(pos);
            }
            las[x] = 0;
            op[x] = i;
        } else ms.insert(i);
        c = 'g';
    }
    puts("-1");
    return 0;
}