'commit'

TangDou/XiTi/1329.cpp

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