[luoguP2983] [USACO10FEB]购买巧克力Chocolate Buying（贪心）

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——代码

 #include <cstdio>
 #include <iostream>
 #include <algorithm>

 int n;
 long long m, ans;
 struct node
 {
     long long x, y;
 }p[];

 inline long long read()
 {
     long long x = , f = ;
     char ch = getchar();
     for(; !isdigit(ch); ch = getchar()) if(ch == '-') f = -;
     for(; isdigit(ch); ch = getchar()) x = (x << ) + (x << ) + ch - '';
     return x * f;
 }

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

 int main()
 {
     int i;
     long long k;
     n = read();
     m = read();
     for(i = ; i <= n; i++) p[i].x = read(), p[i].y = read();
     std::sort(p + , p + n + , cmp);
     for(i = ; i <= n; i++)
     {
         k = m / p[i].x;
         if(k > p[i].y)
         {
             m -= p[i].x * p[i].y;
             ans += p[i].y;
         }
         else
         {
             ans += k;
             break;
         }
     }
     printf("%lld\n", ans);
     return ;
 }