剑指offer面试题36：数组中的逆序对

#include "iostream"using namespace std;int InversePairsCore(int* data,int* copy,int start,int end){if (start==end){copy[start] = data[start];return 0;}int length = (end - start) / 2;int left = InversePairsCore(copy, data, start, start + length);int right = InversePairsCore(copy, data, start + length + 1, end);int i = start + length;int j = end;int indexCopy = end;int count = 0;while (i>=start&&j>=start+length+1){if (data[i]>data[j]){copy[indexCopy--] = data[i--];count += j - start - length;}else{copy[indexCopy--] = data[j--];}}for (; i >= start; --i)copy[indexCopy--] = data[i];for (; j >=start + length + 1; --j)copy[indexCopy--] = data[j];return left + right + count;}int InversePairs(int* data, int length){if (data == NULL || length < 0)return 0;int *copy = new int[length];for (int i = 0; i < length; i++)copy[i] = data[i];int count = InversePairsCore(data, copy, 0, length - 1);delete[] copy;return count;}int main(){int a[] = { 7, 5, 6, 4 };cout << InversePairs(a, 4);system("pause");return 0;}