import java.util.Scanner;

class Pencil { private int price; private int num;

public Pencil() {
}

public Pencil(int price, int num) {
    this.price = price;
    this.num = num;
}

public int getPrice() {
    return price;
}

public void setPrice(int price) {
    this.price = price;
}

public int getNum() {
    return num;
}

public void setNum(int num) {
    this.num = num;
}

}

public class Main { public static void main(String[] args) { //定义需要的铅笔数量 Scanner sc = new Scanner(System.in); int need = sc.nextInt();

    //定义分别购买三种铅笔的花费
    int []expenditure = new int[3];

    //定义三种铅笔的价格与数量
    Pencil [] arr = new Pencil[3];
    for (int i = 0; i < arr.length; i++) {
        int count= sc.nextInt();
        int price = sc.nextInt();
        arr[i] = new Pencil(price, count);
    }

    for (int i = 0; i < arr.length; i++) {
        //用temp来代替need，防止need被修改
        int temp = need;

        //用while循环来判断分别需要多少钱
        while (temp > 0) {
            temp = temp - arr[i].getNum();
            expenditure[i] += arr[i].getPrice();
        }

    }

    //输出最少花费
    //定义min
    int min = expenditure[0];
    for (int i = 1; i < expenditure.length; i++) {
        if (expenditure[i] < min) {
            min = expenditure[i];
        }
    }
    System.out.println(min);
}

}

暴力解题法

#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,a1,a2,b1,b2,c1,c2,ta,tb,tc;
    cin>>n>>a1>>a2>>b1>>b2>>c1>>c2;
    if(n%a1==0)
        ta=n/a1*a2;
    else
        ta=(n/a1+1)*a2;
    if(n%b1==0)
        tb=n/b1*b2;
    else
        tb=(n/b1+1)*b2;
    if(n%c1==0)
        tc=n/c1*c2;
    else
        tc=(n/c1+1)*c2;
    int mix=ta;
    if(tb<=mix)
        mix=tb;
    if(tc<=mix)
        mix=tc;
    cout<<mix;
    return 0;
}

#include<bits/stdc++.h> using namespace std; long long n,a,b,d,mx=INT_MAX; int main(){ cin>>n; for(int i=1;i<=3;i++) { cin>>a>>b; d=ceil(double(n)/a)*b; mx=min(mx,d); } cout<<mx; return 0; }