23 lines
553 B
C++
23 lines
553 B
C++
#include <bits/stdc++.h>
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using namespace std;
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int n;
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string a, B;
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int ans; //极限值是20000*20000=400000000,是不会爆int的
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unordered_map<string, int> _map;
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int main() {
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cin >> n;
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for (int i = 1; i <= n; i++) {
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cin >> a >> b;
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//如果反过来掉过去都一样，就不用计算
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string a1 = a.substr(0, 2), b1 = b.substr(0, 2);
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if (a1 != b1) {
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_map[a1 + b1]++;
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ans += _map[b1 + a1];
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}
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}
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//输出结果
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cout << ans << endl;
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return 0;
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} |