You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
42 lines
936 B
C++
42 lines
936 B
C++
#include <algorithm>
|
|
#include <cstdio>
|
|
#include <cstring>
|
|
#include <stdint.h>
|
|
#define lowbit(x) ((x) & -(x))
|
|
const int N = 500005;
|
|
int sum[N];
|
|
int query(int x)
|
|
{
|
|
int ans = 0;
|
|
for (; x; x -= lowbit(x)) ans += sum[x];
|
|
return ans;
|
|
}
|
|
void update(int x, int y)
|
|
{
|
|
for (; x <= N; x += lowbit(x)) sum[x] += y;
|
|
}
|
|
struct abcd
|
|
{
|
|
int val, pos;
|
|
bool operator<(const abcd &rhs) const { return val < rhs.val; }
|
|
} nodes[N];
|
|
int map[N];
|
|
int main()
|
|
{
|
|
int n;
|
|
while (~scanf("%d", &n) && n)
|
|
{
|
|
memset(sum, 0, sizeof(sum));
|
|
for (int i = 1; i <= n; i++) scanf("%d", &nodes[i].val), nodes[i].pos = i;
|
|
std::sort(nodes + 1, nodes + n + 1);
|
|
for (int i = 1; i <= n; i++) map[nodes[i].pos] = i;
|
|
int64_t ans = 0;
|
|
for (int i = 1; i <= n; i++)
|
|
{
|
|
update(map[i], 1);
|
|
ans += i - query(map[i]);
|
|
}
|
|
printf("%lld\n", ans);
|
|
}
|
|
return 0;
|
|
} |