1428 - Ping pong

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cstdlib>
using namespace std;
const int INF = 100000 + 7;
const int maxn = 20000 + 7;
typedef long long LL;
int T, n, MAX;
int left_[maxn], right_[maxn];
int d[maxn];
int c[INF];

int lowbit(int x) { return x & (-x); }

LL sum(int x) {
LL res = 0;
while(x > 0) {
res += c[x];
x -= lowbit(x);
}
return res;
}

void add(int k) {
while(k <= INF) {
c[k] += 1;
k += lowbit(k);
}
}

int main() {
scanf("%d", &T);
while(T--) {
memset(d, 0, sizeof(d));
memset(c, 0, sizeof(c));
memset(left_, 0, sizeof(left_));
memset(right_, 0, sizeof(right_));
MAX = -10000;
scanf("%d", &n);
for(int i = 0; i < n; ++i) {
scanf("%d", &d[i]);
add(d[i]);
MAX = max(MAX, d[i]);
left_[i] = sum(d[i] - 1);
right_[i] = max(0LL, sum(MAX) - sum(d[i]));
}
LL ans = 0;
for(int i = 0; i < n; ++i) {
if(i == 0 || i == n - 1) continue;
ans += left_[i] * ((sum(MAX) - sum(d[i])) - right_[i]);
ans += right_[i] * (sum(d[i]-1) - left_[i]);
}
printf("%lld\n", ans);
}
return 0;
}