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：
