题解 | False coin

#include <iostream>
#include<vector>
#include<algorithm>
using namespace std;
//未处理0，可能轻-1，可能重2，真1
//=说明两边都是真；不等号说明假在两边，其他真；同一硬币两次判断相反说明真。
//只对未测和非真进行统计，数目为一则输出结果，否则输出零。
vector<int>weight;
int n;
void deal() {
    int a;
    cin >> a;
    vector<int>left(a), right(a);
    for (int j = 0; j < a; j++) {
        cin >> left[j];
    }
    for (int j = 0; j < a; j++) {
        cin >> right[j];
    }
    char op;
    cin >> op;
    if(op=='='){
        for(int w:left){
            weight[w]=1;
        }
        for(int w:right){
            weight[w]=1;
        }
    }
    else if(op=='<'){
        for(int w:left){
            if(weight[w]==0) weight[w]=-1;
            else if(weight[w]==2) weight[w]=1;
        
        }
        for(int w:right){
            if(weight[w]==0) weight[w]=2;
            else if(weight[w]==-1) weight[w]=1;
        
        }
        for(int i=1;i<=n;i++){//出现不等号说明其他硬币都是真的
            if(find(left.begin(),left.end(),i)==left.end()&&find(right.begin(),right.end(),i)==right.end()){
                weight[i]=1;
            }
        }
    }
    else if(op=='>'){
        for(int w:left){
            if(weight[w]==0) weight[w]=2;
            else if(weight[w]==-1) weight[w]=1;
        
        }
        for(int w:right){
            if(weight[w]==0) weight[w]=-1;
            else if(weight[w]==2) weight[w]=1;
        
        }
        for(int i=1;i<=n;i++){
            if(find(left.begin(),left.end(),i)==left.end()&&find(right.begin(),right.end(),i)==right.end()){
                weight[i]=1;
            }
        }
    }

}
int main() {
    int  k;
    while (cin >> n >> k) { // 注意 while 处理多个 case
        weight=vector<int>(n+1,0);
        for (int i = 0; i < k; i++) {
            deal();
        }
        vector<int>res(4,0);
        int f;
        for(int i=1;i<=n;i++){
            res[weight[i]+1]++;
            if(weight[i]!=1){
                f=i;
            }
        }
        if(res[2]!=n-1){
            cout<<0<<endl;
        }
        else{
            cout<<f<<endl;
        }

    }
}
// 64 位输出请用 printf("%lld")