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35 lines
802 B
C++
35 lines
802 B
C++
#pragma GCC optimize(2)
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#include <bits/stdc++.h>
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using namespace std;
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long long n, ans, x[3005], y[3005], t, l;
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double b[10000005];
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int main() {
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std::ios::sync_with_stdio(false);
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cin >> n;
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ans = n * (n - 1) * (n - 2) / 6;
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for (int i = 1; i <= n; i++) {
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cin >> x[i] >> y[i];
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t = 0;
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l = 1;
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for (int j = i - 1; j > 0; j--) {
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b[++t] = x[i] - x[j] ? (double)(y[i] - y[j]) / (double)(x[i] - x[j]) : 0x3f3f3f3f3f3f3f3f;
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}
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sort(b + 1, b + 1 + t);
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for (int j = 2; j <= t; j++) {
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if (b[j] == b[j - 1]) {
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l++;
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} else {
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ans -= l * (l - 1) / 2;
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l = 1;
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}
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}
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ans -= l * (l - 1) / 2;
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}
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cout << ans << endl;
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return 0;
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}
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