题解 | #单词识别#

map底层采用红黑树使用
for (auto it = alpha.begin(); it != alpha.end(); advance(it, 1))
可以从小到大按照字典序排序

#include <bits/stdc++.h>
using namespace std;
string to_lower(string s) {
    for (char& ch : s)ch = tolower(ch);
    return s;
}
int main() {
    map<string, int> alpha;
    string s;
    while (cin >> s) {
        if (s.back() == '.')s = s.substr(0, s.size() - 1);
        transform(s.begin(), s.end(), s.begin(), ::tolower);
        alpha[s]++;
    }
    for (auto it = alpha.begin(); it != alpha.end(); advance(it, 1)) {
        cout << it->first << ":" << it->second << endl;
    }
    return 0;
}
// 64 位输出请用 printf("%lld")