蓝桥杯 贪心模板 _算法提高 快乐司机

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstdlib>
using namespace std;

const int maxn = 10000 + 200;
struct Lorry {
    float weight;
    float value;
    float pro;
    Lorry(float w = 0, float v = 0, float pro = 0) :
        weight(w), value(v), pro(pro) {}
} lorry[maxn]; 

//按价值率降序排序
bool cmp(const Lorry& a, const Lorry& b)
{
    return a.pro > b.pro;
}

void solve();

void solve()
{
    int n;
    float w; //物品数量, 核载重量
    float ans = 0;
    scanf("%d", &n);
    cin >> w;
    for (int i = 0; i < n; i++) {
        cin >> lorry[i].weight >> lorry[i].value;
        lorry[i].pro = lorry[i].value / lorry[i].weight;
    }
    //价值高的在前
    sort(lorry, lorry + n, cmp);

    for (int i = 0; i < n; i++)
    {
        if (w == 0) break;
        //w > l[i].weight 放心减就好了
        if (w - lorry[i].weight > 0) {
            w -= lorry[i].weight;
            ans += lorry[i].value;
        } else {
            //否则..全部用来给w, 还有剩余，单价最高嘛
            ans += lorry[i].pro * w;
            lorry[i].weight -= w;
            w = 0;
        }
    }
    printf("%.1f\n", ans);
}

int main()
{
    solve();
    return 0;
}

//好多简单题贪心算法，都需要定义结构体来组合数据， 并且提供比较函数，方便sort函数排序， 像这样~

struct Lorry {
    float weight;
    float value;
    float pro;        //单价
    Lorry(float w = 0, float v = 0, float pro = 0) :
        weight(w), value(v), pro(pro) {}
} lorry[maxn]; 

//按价值率降序排序
bool cmp(const Lorry& a, const Lorry& b)
{
    return a.pro > b.pro;
}

//来用这个模板写一题，Codevs上的快乐牛奶

#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <vector>
using namespace std;

const int maxM = 5000 + 20;   //农民数量
struct Milk {
    int amount;
    int value;
    Milk(int m = 0, int v = 0) : amount(m), value(v) {}
} Farmer[maxM];

void solve();

//按照价格 升序排序
bool cmp(const Milk& a, const Milk& b) {
    return a.value < b.value;
}

void solve()
{
    int N, M;   // N -- 需求, M -- 农民数目
    int ans = 0;
    scanf("%d%d", &N, &M);
    //硬币问题
    //最少价格, 刚刚好 N 数量
    //应该每次 挑选 单价最低的
    for (int i = 0; i < M; i++) {
        //输入价格 and 数量
        scanf("%d%d", &Farmer[i].value, &Farmer[i].amount);
    }
    //按照价格 升序排序
    sort(Farmer, Farmer + M, cmp);
    for (int i = 0; i < M; i++)
    {//每次选价格低的先 大于0再执行下面，如果刚刚好为0,则不好直接退出
        if (N - Farmer[i].amount > 0) {
            N -= Farmer[i].amount;
            ans += Farmer[i].amount*Farmer[i].value;
        } else {
            for (int j = 1; j <= Farmer[i].amount; j++) {
                if (N - j == 0) {
                    N = 0;
                    ans += Farmer[i].value * j;
                    printf("%d\n", ans);
                    return;
                }
            }
        }
    }
    printf("%d\n", ans);

}

int main()
{
    solve();
    return 0;
}