Educational Codeforces Round 52 (Rated for Div. 2)【A,B,C】【C题：贪心+约束差分模板】

 水题。仔细看题

#include<bits/stdc++.h>
 
using namespace std;
#define int long long
signed main(){
    int _;
    cin>>_;
    while(_--){
        int s,a,b,c;
        cin>>s>>a>>b>>c;
        int ans=0;
        ans=(s/(a*c))*a+(s/(a*c))*b+(s%(a*c))/c;
        cout<<ans<<'
';
    }
    
    return 0;
} 

 思路：找规律

#include<bits/stdc++.h>
 
using namespace std;
#define int long long
signed main(){
    
    int n,m;
    cin>>n>>m;
    
    int ans1=n-min(m*2,n);
    int ans2=0;
    for(int i=0;;i++){
        int cnt=(i-1)*(i)/2;
        if(cnt>=m){
            ans2=i;break;
        }
    }
    cout<<ans1<<" "<<n-ans2;
    return 0;
}

 思路：约束差分进行O（n）的处理。然后贪心。

#include<bits/stdc++.h>

using namespace std;
#define int long long
#define N 666666
int H[N];int vis[N];//vis数组的定义：高度为I的有VIS[I]个
signed main(){
    int n,k;
    cin>>n>>k;
    int maxn=0;
    for(int i=1;i<=n;i++){
        scanf("%lld",&H[i]);
        maxn=max(maxn,H[i]);
        vis[0]++;
        vis[H[i]+1]--;
    }
    for(int i=1;i<=N;i++){
        vis[i]+=vis[i-1];
    }
    int ans=0;int sum=0;
/*    for(int i=1;i<=maxn;i++){//
        cout<<vis[i]<<" ";
    }
    cout<<'
';
    */
    for(int i=maxn;i>=1;i--){
        if(vis[i]>=n){
            if(sum) 
                ans++;
            break;
        }
        if(sum+vis[i]<=k){
            sum+=vis[i];
        }else{
            ans++;
            sum=vis[i];
        }
    }
    cout<<ans;
    return 0;
}