30 lines
650 B
C++
30 lines
650 B
C++
#include <bits/stdc++.h>
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#include <unordered_map>
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using namespace std;
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int main() {
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int n;
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cin >> n;
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unordered_map<int, int> _map;
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for (int i = 0; i < n; i++) {
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int c;
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cin >> c;
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if (c > 0) {
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_map[c] = 1;
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} else {
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if (_map.count(abs(c)) > 0) {
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_map[abs(c)]++;
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}
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}
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}
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//遍历map，找到值为2的
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int count = 0;
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unordered_map<int, int>::iterator it = _map.begin();
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while (it != _map.end()) {
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if (it->second == 2) count++;
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it++;
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}
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cout << count << endl;
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return 0;
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} |