Frederick Chen
10fe6aa33b
https://codeforces.com/problemset/problem/1922/B Signed-off-by: Frederick Chen <seventeen@ohdragonboi.cn>
20 lines
541 B
C++
20 lines
541 B
C++
#include<iostream>
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using namespace std;
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long long t, n, a[300005];
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long long cnt[300005], s[300005], ans;
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int main(){
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ios::sync_with_stdio(0);
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cin >> t;
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while(t -- ){
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cin >> n;
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ans = 0;
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for(int i = 0; i <= n; i ++ ) cnt[i] = s[i] = 0;
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for(int i = 1; i <= n; i ++ ) cin >> a[i], cnt[a[i]] ++ ;
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for(int i = 0; i <= n; i ++ ) ans += cnt[i] * (cnt[i] - 1) * (cnt[i] - 2) / 6, s[i] = (i == 0 ? 0 : s[i - 1]) + cnt[i];
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for(int i = 1; i <= n; i ++ ) ans += cnt[i] * (cnt[i] - 1) / 2 * s[i-1];
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cout << ans << "\n";
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}
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return 0;
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}
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