Yogurt factory POJ - 2393 (贪心)

待我称王封你为后i 2022-03-08 10:16 137阅读 0赞

The cows have purchased a yogurt factory that makes world-famous Yucky Yogurt. Over the next N (1 <= N <= 10,000) weeks, the price of milk and labor will fluctuate weekly such that it will cost the company C\_i (1 <= C\_i <= 5,000) cents to produce one unit of yogurt in week i. Yucky's factory, being well-designed, can produce arbitrarily many units of yogurt each week.  
  
Yucky Yogurt owns a warehouse that can store unused yogurt at a constant fee of S (1 <= S <= 100) cents per unit of yogurt per week. Fortuitously, yogurt does not spoil. Yucky Yogurt's warehouse is enormous, so it can hold arbitrarily many units of yogurt.  
  
Yucky wants to find a way to make weekly deliveries of Y\_i (0 <= Y\_i <= 10,000) units of yogurt to its clientele (Y\_i is the delivery quantity in week i). Help Yucky minimize its costs over the entire N-week period. Yogurt produced in week i, as well as any yogurt already in storage, can be used to meet Yucky's demand for that week.

Input

\* Line 1: Two space-separated integers, N and S.  
  
\* Lines 2..N+1: Line i+1 contains two space-separated integers: C\_i and Y\_i.

Output

\* Line 1: Line 1 contains a single integer: the minimum total cost to satisfy the yogurt schedule. Note that the total might be too large for a 32-bit integer.

Sample Input

4 5
    88 200
    89 400
    97 300
    91 500

Sample Output

126900

解题思路:

把本周与前一周的价格进行比较,如果本周的价格>前一周的价格+运费,那么我们就把这一周的价格设定为前一周的价格+存储费

注意如果存储多周的话,那么总存储费就是存储费\*周数

#include <iostream>
    #include <algorithm>
    #include <string.h>
    #include <stdio.h>
    using namespace std;
    long long totalCost = 0;
    const int MAXN = 10010;
    int N, S;
    struct uYogurt {
    	int C_i;
    	int Y_i;
    }uYogurts[MAXN];
    
    int main() {
    	while (scanf("%d %d", &N, &S) != EOF) {
    		totalCost = 0;
    		int minPrice = 0;
    		for (int i = 0; i < N; ++i) {
    			scanf("%d %d", &uYogurts[i].C_i, &uYogurts[i].Y_i);
    		}
    		//贪心策略:从前一周开始生产还是本周开始生产?如果从前一周开始生产的话,本周的价格就是前一周生产的价格+存储费
    		for (int i = 1; i < N; ++i) { 
    			uYogurts[i].C_i = min(uYogurts[i].C_i, uYogurts[i - 1].C_i + S);
    		}
    		//最后运行
    		for (int i = 0; i < N; ++i) {
    			totalCost += uYogurts[i].C_i*uYogurts[i].Y_i;
    		}
    		printf("%lld\n", totalCost);
    	}
    	return 0;
    }