C题乱搞过去了

#include<bits/stdc++.h>
using namespace std;
#define int long long
int n,m,k,ii[5000007],gg[20007][205];
vector<int>g[205];
unsigned seed;
unsigned rnd(){
	unsigned ret=seed;
	seed^=seed<<13;
	seed^=seed>>17;
	seed^=seed<<5;
	return ret;
}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin>>n>>m>>k>>seed;
    for(int i=1;i<=k;i++){
        int op=(rnd()%2)+1;
        if(op==1){
            int j=(rnd()%m)+1;
            int x=(rnd()%(n*m))+1;
            g[j].push_back(i);
            ii[i]=x;
        }
        else{
            int a=(rnd()%n)+1;
            int b=(rnd()%m)+1;
            gg[a][b]=i;
        }
    }
    int res=0;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            if(gg[i][j]==0){
                if(g[j].size()>=1)res=res^(ii[g[j][0]]*((i-1)*m+j));
                continue;
            }
            int pos=lower_bound(g[j].begin(),g[j].end(),gg[i][j])-g[j].begin();
            if(pos<g[j].size())res=res^(ii[g[j][pos]]*((i-1)*m+j));
        }
    }
    cout<<res<<'\n';
    return 0;
}

如果去掉36到39行会超时，加上就可以卡过去。https://ac.nowcoder.com/acm/contest/view-submission?submissionId=74244790