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58 lines (52 loc) · 1.37 KB
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/*******************************************************************************
> File Name: 180.cpp
> Author: sillyplus
> Mail: oi_boy@sina.cn
> Created Time: Sat May 30 21:28:12 2015
*******************************************************************************/
#include <bits/stdc++.h>
using namespace std;
const int MAXN = 66000;
long long inversed_pair(int a[], int n) {
if (n == 1) return 0;
long long sum = 0;
int mid = n / 2;
sum += inversed_pair(a, mid);
sum += inversed_pair(a+mid, n-mid);
int *b = new int[n];
memcpy(b, a, n * sizeof(int));
for (int i1 = 0, i2 = mid, i = 0; i1 < mid || i2 < n; ++i) {
if (i2 == n) {
a[i] = b[i1++];
sum += i2 - mid;
} else if (i1 == mid) {
a[i] = b[i2++];
} else if (b[i1] < b[i2]) {
a[i] = b[i1++];
sum += i2 - mid;
} else {
a[i] = b[i2++];
}
}
delete [] b;
return sum;
}
int f[MAXN];
int main(int argc, char* argv[]) {
int n;
cin >> n;
for (int i = 0; i < n; ++i) {
scanf("%d", f+i);
}
long long ans = inversed_pair(f, n);
long long tmp = 1;
f[n] = -1;
for (int i = 1; i <= n; ++i) {
if (f[i] != f[i-1]) {
ans = ans - (tmp * (tmp-1) / 2);
tmp = 1;
} else tmp++;
}
cout << ans << endl;
return 0;
}