POJ_2299(归并排序)

#include <cstdlib> #include <iostream> #include <cstdio> using namespace std; const int MAX = 500001; int value[MAX]; int temp[MAX]; __int64 result = 0; void merge(int left, int mid, int right) { int k = 0; int i=left; int j=mid + 1; while(i<=mid && j<=right) { if(value[i] <= value[j]) temp[k++] = value[i++]; else { temp[k++] = value[j++]; result += mid - i + 1; } } while(i <= mid) temp[k++] = value[i++]; while(j <= right) temp[k++] = value[j++]; for(int i=0; i<=right - left; i++) value[i + left] = temp[i]; } void mergeSort(int left, int right) { if(left < right) { int mid = (left + right) >> 1; mergeSort(left, mid); mergeSort(mid + 1, right); merge(left, mid, right); } } int main(int argc, char *argv[]) { int n, i; //freopen("input.txt", "rt", stdin); //freopen("output.txt", "wt", stdout); while(scanf("%d", &n) && n != 0) { result = 0; for(int i=0; i<n; i++) scanf("%d", &value[i]); mergeSort(0, n - 1); printf("%I64d/n", result); } return EXIT_SUCCESS; }