bzoj2014[Usaco2010 Feb]Chocolate Buying
题意：
n种巧克力，每种有个单价和最多能买几块，问有B块钱一共最多能买几块。n≤100000
题解：
贪心，按单价排序。
代码：
1 #include <cstdio> 2 #include <cstring> 3 #include <algorithm> 4 #define ll long long 5 #define inc(i,j,k) for(int i=j;i<=k;i++) 6 #define maxn 100010 7 using namespace std; 8 9 inline ll read(){ 10 char ch=getchar(); ll f=1,x=0; 11 while(ch<'0'||ch>'9'){if(ch=='-')f=-1; ch=getchar();} 12 while(ch>='0'&&ch<='9')x=x*10+ch-'0',ch=getchar(); 13 return f*x; 14 } 15 int n; ll b,ans; 16 struct nd{ll p,c;}; nd nds[maxn]; 17 inline bool cmp(const nd &a,const nd &b){return a.p<b.p;} 18 int main(){ 19 n=read(); b=read(); inc(i,1,n)nds[i]=(nd){read(),read()}; sort(nds+1,nds+1+n,cmp); 20 inc(i,1,n){ 21 ll use=min(nds[i].c,b/nds[i].p); 22 b-=use*nds[i].p; ans+=use; if(use!=nds[i].c)break; 23 } 24 printf("%lld",ans); return 0; 25 }
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