树状数组求逆序和模板

C++ code:

#include <iostream>

#include <cstdio>

#include <algorithm>

#include <cstring>

#define lowbit(i) (i & -i);



using namespace std;



struct lines

{

	long l, r, i;

}line[30001];

bool cmp_1(lines, lines);

bool cmp_2(lines, lines);



int main()

{

	long A, B, n, i, k, b, T[30001], m, j;



	while(scanf("%ld%ld", &A, &B) == 2)

	{

		scanf("%ld", &n);

		for(i = 1; i <= n; i++)

		{

			scanf("%ld%ld", &k, &b);

			line[i].l = k * A + b;

			line[i].r = k * B + b;

			T[i] = lowbit(i);

		}

		sort(line + 1, line + n + 1, cmp_1);

		for(i = 1; i <= n; i++)

			line[i].i = i;

		sort(line + 1, line + n + 1, cmp_2);

		T[0] = m = 0;

		for(i = 1; i <= n; i++)

		{

			j = line[i].i - 1;

			while(j)

			{

				m += T[j];

				j -= lowbit(j);

			}

			j = line[i].i;

			while(j <= n)

			{

				T[j]--;

				j += lowbit(j);

			}

		}

		printf("%ld\n", n + m + 1);

	}



	return 0;

}



bool cmp_1(lines a, lines b)

{

	return a.l > b.l;

}



bool cmp_2(lines a, lines b)

{

	return a.r > b.r;

}