题解 | #删除字符串中出现次数最少的字符#

#include <iostream>
#include <string>
#include <cctype>
#include <algorithm>
#include <unordered_map>
#include <climits>
using namespace std;

string delete_ch(const string& str) {
    string result = str;
    unordered_map<char, int> mymap;

    transform(result.begin(), result.end(), result.begin(),
                   [](unsigned char c){ return tolower(c); }); //lambda表达式,C++新特性

    for(auto ch: result) {
        if (isalpha(ch)) {
            ch = tolower(ch);
            mymap[ch]++;
        }        
    }
    
    int mincount = INT_MAX;
    char min_cn = '\0';

    for (auto count: mymap) {
        mincount = min(mincount, count.second);
    }

    for (const auto& it : mymap) {
        if(it.second == mincount) {
            // 使用erase-remove惯用法删除所有出现的指定字符
            min_cn = it.first;
            result.erase(std::remove(result.begin(), result.end(), min_cn), result.end());
        }
    }
    return result;
}

int main() {
    string input;
    cin >> input;
    cout << delete_ch(input) << endl;
    

    return 0;
}