求一下逆序数，因为冒泡交换的准则是大于或者小于，逆序数累加的准则同样也是。
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#include<iostream>
using namespace std; long long cnt; void merge(int array[], int left, int mid, int right) { int* temp = new int[right - left + 1]; int i, j, p; for (i = left, j = mid + 1, p = 0; i <= mid&&j <= right; p++) { if (array[i] <= array[j])temp[p] = array[i++]; else temp[p] = array[j++], cnt += (mid - i + 1); } while (i <= mid)temp[p++] = array[i++]; while (j <= right)temp[p++] = array[j++]; for (i = left, p = 0; i <= right; i++)array[i] = temp[p++]; delete temp; } void mergesort(int array[], int left, int right) { if (left == right)array[left] = array[right]; else { int mid = (left + right) / 2; mergesort(array, left, mid); mergesort(array, mid + 1, right); merge(array, left, mid, right); } } int main() { int n; while (cin >> n, n) { int array[500005]; cnt = 0; for (int i = 0; i<n; i++) cin >> array[i]; mergesort(array, 0, n - 1); cout << cnt << endl; } return 0; } |
作者：zhengnanlee 发表于2013-12-1 0:43:42 原文链接
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