BFS+暴力if判断

#include <iostream>
#include <queue>
#include <set>
#include <unordered_map>

using namespace std;

void func(set<pair<int,int>> & res , queue<pair<int,int>>& q, int n);

int main(){
    int n,k,x,y;
    cin>>n>>k>>x>>y;
    set<pair<int,int>> res;
    queue<pair<int,int>> q;
    q.push({x,y});
    res.insert({x,y});
    while(k-- && !q.empty()){
        func(res,q,n);
    }
    cout<<res.size()<<endl;
}

void func(set<pair<int,int>>& res , queue<pair<int,int>>& q,int n){
    int it = q.size();
    if(it == 0) return;

    while(it--){
    int a = q.front().first;
    int b = q.front().second;
    q.pop();
    if(b+2<=n){
        if(a-1 >= 1 && !res.count({a-1,b+2})){
            res.insert({a-1,b+2});
            q.push({a-1,b+2});
        }
        if(a+1 <= n && !res.count({a+1,b+2})){
            res.insert({a+1,b+2});
            q.push({a+1,b+2});
        }
    }
    if(b+1<=n){
        if(a-2 >= 1 && !res.count({a-2,b+1})){
            res.insert({a-2,b+1});
            q.push({a-2,b+1});
        }
        if(a+2 <= n && !res.count({a+2,b+1})){
            res.insert({a+2,b+1});
            q.push({a+2,b+1});
        }
    }
    if(b-1>=1){
        if(a-2 >= 1 && !res.count({a-2,b-1})){
            res.insert({a-2,b-1});
            q.push({a-2,b-1});
        }
        if(a+2 <= n && !res.count({a+2,b-1})){
            res.insert({a+2,b-1});
            q.push({a+2,b-1});
        }
    }
    if(b-2>=1){
        if(a-1 >= 1 && !res.count({a-1,b-2})){
            res.insert({a-1,b-2});
            q.push({a-1,b-2});
        }
        if(a+1 <= n && !res.count({a+1,b-2})){
            res.insert({a+1,b-2});
            q.push({a+1,b-2});
        }
    }
}
}