c++ 统计 vector 每个元素出现的次数 (C++ count the number of occurrences of each element in vector)

参考： https://stackoverflow.com/questions/1204313/counting-occurrences-in-a-vector

 1 vector<int> blockType = { 2, 3, 4, 5, 2, 2, 1, 1, 5 };
 2 typedef map<int, int> mapIntInt;
 3 mapIntInt mapCount;
 4 for (int i = 0; i < blockType.size(); ++i) {
 5     mapIntInt::iterator iterator(mapCount.find(blockType[i]));
 6     if (iterator != mapCount.end()) {
 7         iterator->second++;
 8     }
 9     else {
10         mapCount[blockType[i]] = 1;
11     }
12 }
13 
14 //两种遍历map的方法
15 for_each(mapCount.begin(), mapCount.end(), [&](pair<int, int> element) {
16     int typeName = element.first;
17     int typeNumber = element.second;
18     cout << typeName << " : " << typeNumber << endl;
19     });
20 
21 cout << "--------------------------------" << endl;
22 
23 for (auto const& element : mapCount)
24 {
25     int typeName = element.first;
26     int typeNumber = element.second;
27     cout << typeName << " : " << typeNumber << endl;
28 }

结果如下：