P2983 [USACO10FEB] buy chocolate

P2983 [USACO10FEB] buy chocolate

answer

Note entitled to open long long 

Greedy strategy: price from low to high, enough to buy up

Evidence to the contrary: If there is a remaining K ", is smaller than K, then the exchange can not lose

           So, before buying K, all cheaper than he can buy finished

 

 

Code

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<string>
#include<cstring>
#include<cstdlib>
#include<queue>

using namespace std;

#define ll long long

inline ll read()
{
    ll ans=0;
    char last=' ',ch=getchar();
    while(ch<'0'||ch>'9') last=ch,ch=getchar();
    while(ch>='0'&&ch<='9') ans=ans*10+ch-'0',ch=getchar();
    if(last=='-') ans=-ans;
    return ans;
}

ll n,b,ans=0;
struct node
{
    ll cost,cow;
}candy[100010];

bool cmp(node x,node y)
{
    return x.cost <y.cost ;
}

int main()
{
    
    n=read();b=read();
    for(ll i=1;i<=n;i++)
    {
        candy[i].cost =read();
        candy[i].cow =read();
    }
    
    sort(candy+1,candy+n+1,cmp);

    for(ll i=1;i<=n;i++)
    {
        if(candy[i].cow==0) continue;
        if(b==0)
        { printf("%lld",ans); return  0 ;}
         IF (Candy [I] .cow <= B / Candy [I] .cost)   // directly multiply the explode 
        { 
            B - = Candy [I] .cost * Candy [I] .cow; 
            ANS + = Candy [I] .cow;
             Continue ; 
        } 
        the else 
        { 
            ANS + = B / Candy [I] .cost;   // not a save enumeration time 
            the printf ( " % LLD " , ANS); return  0 ; 
        } 
    } 
    the printf ( " % LLD " , ANS); 
    
    return  0;
}