USACO 1.3 Mixing Milk (快排+贪心)

#include <stdio.h>#define DEBUG 0#define TESTCASES 9#define MAX_FARMERS 5000int milkNeeded;int numOfFarmers;typedef struct Farmer{int price;int milk;}Farmer;Farmer farmers[MAX_FARMERS + 1];void sortFarmersAccordingToPrice(int first, int last){while (first < last){Farmer pivotFarmer = farmers[first];int pivotPrice = farmers[first].price;int left = first;int right = last;while (left < right){while (left < right && farmers[right].price >= pivotPrice)right--;farmers[left] = farmers[right];while (left < right && farmers[left].price <= pivotPrice)left++;farmers[right] = farmers[left];}farmers[left] = pivotFarmer;int pivot = left;sortFarmersAccordingToPrice(first, pivot);first = pivot + 1;}}int mix(){int minPrice = 0;int milkMixed = 0;int farmer;for (farmer = 1; farmer <= numOfFarmers; farmer++){if (milkMixed  + farmers[farmer].milk >= milkNeeded){minPrice += farmers[farmer].price * (milkNeeded - milkMixed);break;} else {milkMixed += farmers[farmer].milk;minPrice += farmers[farmer].price * farmers[farmer].milk;}}return minPrice;}int main(){#if DEBUGint testCase;for (testCase = 1; testCase <= TESTCASES; testCase++){char inputFileName[20] = "milk.inX";inputFileName[7] = '1' +  (testCase - 1);freopen(inputFileName, "r", stdin);printf("\n#%d\n", testCase);#endifscanf("%d %d", &milkNeeded, &numOfFarmers);int farmer;for (farmer = 1; farmer <= numOfFarmers; farmer++)scanf("%d %d", &farmers[farmer].price, &farmers[farmer].milk);sortFarmersAccordingToPrice(1, numOfFarmers);int minPrice = mix();printf("%d\n", minPrice);#if DEBUG}#endifreturn 0;}