看了大佬题解,学到了

Code

#include <bits/stdc++.h>

using namespace std;

int m,k,x;
char s[10];

struct cmp{
    bool operator () (const int & x,const int & y) const {
        if(abs(x-y)<=k) return false;
        return x < y;
    }
};
set<int,cmp> se;

int main(){
    scanf("%d %d",&m,&k);
    while(m--){
        scanf("%s",s);scanf("%d",&x);
        if(s[0]=='a') se.insert(x);
        else if(s[0]=='d') se.erase(x);
        else{
            if (se.find(x)!=se.end()) puts("Yes");
            else puts("No"); 
        }
    }

    return 0;
}