用快排思路解决逆序对问题

#include<iostream>#include<fstream>#define rep(i, n) for(i=0;i<n;i++)#define repi(i,l,n) for(i=l;i<=r;i++)using namespace std;void quicksort(int l, int r);int a[100];int b[100];int hit;int main(){int i, k;cin >> k;rep(i, k) cin >> a[i];quicksort(0, k - 1);rep(i, k) cout << a[i];cout << hit << endl;getchar(); getchar(); //crash}void quicksort(int l, int r){if (l < r){int round = l + rand() % (r - l + 1);int set = a[round];int i, al = 0, br = 0, il = l, ir, count = 0;repi(i, l, r){if (a[i]<set) count++;}b[count + l] = set;ir = count + 1+l;repi(i, l, r){if (a[i] > set){b[ir++] = a[i];al++;if (i < round)hit++;}else if (a[i] < set){b[il++] = a[i];br++;if (i>round)hit++;hit += al;}}repi(i, l, r){a[i] = b[i];}quicksort(l, count);quicksort(count + 1, r);}}