华为oj之字符统计(按出现次数由多到少的顺序进行输出)

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

bool comp(pair<char,int> a, pair<char,int> b)  // 重载sort函数的自定义比较函数comp
{
    if(a.second > b.second)
        return true;
    else if(a.second == b.second && a.first < b.first)
        return true;
    else return false;
}

int main()
{
    string str;
    unordered_map<char, int> countMap;

    while(getline(cin,str))
    {
    for(int i=0; i <= str.length()-1; i++)
        {
             if(countMap.find(str[i]) == countMap.end())
            {
                countMap[str[i]] = 1;
            }
            else
            {
                countMap[str[i]]++;
            }        
        }

    vector<pair<char, int>> elems(countMap.begin(), countMap.end());
    sort(elems.begin(), elems.end(), comp);  // 使用sort对hash表进行排序

    for(vector<pair<char, int>>::iterator it=elems.begin(); it != elems.end(); it++)
    {
        cout<<it->first;
    }
    cout<<endl;
    countMap.clear();
    }
    return 0;
}

测试用例1: 8v26ktzk069lm400061m0v965we88850o6omqi532ktir6esb55t0kqm026y8rk63aj82kcx48gd1tiylvs0xo32zem65q7z5ce2185d2ascz62a2p3ajr45h637t2p290lc043gicp5ldzzmx2

测试用例2:
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