ABC210(A-C)

A

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,a,x,y;
    cin>>n>>a>>x>>y;
    if(n<=a)cout<<n*x<<endl;
    else cout<<a*x+(n-a)*y<<endl;
    return 0;
    
}

B

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin>>n;
    string s;
    cin>>s;
    int l=s.length();
    int i;
    for(i=0;i<l;i++){
        if(s[i]=='1')break;
    }
    if(i%2==0)cout<<"Takahashi"<<endl;
    else cout<<" Aoki"<<endl;
    return 0;
}

C

#include<bits/stdc++.h>
#define ll long long
using namespace std;
int main()
{
    ll n,k;
    cin>>n>>k;
    ll num[n];
    map<ll,ll> mp;
    for(ll i=0;i<n;i++){
        cin>>num[i];
    }
    ll max=0;
    for(ll i=0;i<k;i++){
        mp[num[i]]++;
    }
    max=mp.size();
    for(ll i=0;i<n-k;i++){
        //cout<<num[i]<<" "<<num[i+1]<<" "<<num[i+2]<<" "<<" "<<" "<<i<<" "<<mp.size()<<endl;
        mp[num[i]]--;
        mp[num[i+k]]++;
        if(mp[num[i]] == 0) mp.erase(num[i]);
        if(mp.size()>max)max=mp.size();
    }
    cout<<max<<endl;
    return 0;
}

学习：

map中值为0时不代表整个键值对删除，要使用earse函数删除

mp.erase(num[i]);