PAT 1070. Mooncake (贪心)

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给出n堆月饼的重量和总价 -- 可求每吨的均价

给出总共的购买量d, 求可获得的最大利润

很简单的。求均价后排降序，从均价最高的开始购入。

1. 基础知识不牢固，scanf double时是用 %lf 标识

2. 对struct排序时，并不调用struct的成员函数< -- 所以重载小于号是没用的，得用友元或者直接在结构声明之外定义函数。

#include <cstdio>#include <vector>#include <algorithm>using namespace std;struct Mooncake{double m_avg;double m_tot;Mooncake(double tot): m_tot(tot) {}//  这么做是不对的//bool operator< (Mooncake a)//{//return m_avg > a.m_avg;//}};bool avg_cmp(const Mooncake& a, const Mooncake& b){return a.m_avg > b.m_avg;}vector<Mooncake> mooncake;int n;double d, tot, price, profit = 0;int main(){scanf("%d%lf", &n, &d);for (int i = 0; i < n; ++ i){scanf("%lf", &tot); // 是%lfmooncake.push_back( Mooncake(tot) );}for (int i = 0; i < n; ++ i){scanf("%lf", &price);mooncake[i].m_avg = price / mooncake[i].m_tot;}//sort(mooncake.begin(), mooncake.end());sort(mooncake.begin(), mooncake.end(), avg_cmp);for (size_t i = 0; i < mooncake.size() && d > 0; ++ i){if (d >= mooncake[i].m_tot){d -= mooncake[i].m_tot;profit += mooncake[i].m_avg * mooncake[i].m_tot;} else{profit += mooncake[i].m_avg * d;d = 0;}}printf("%.2lf\n", profit);return 0;}

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