题解 | #单词识别#

#include <iostream>
#include <string>
#include <vector>
#include <map>
#include <utility>
#include <algorithm>

using namespace std;
//自定义stable_sort()的仿函数，比较count
struct Greater
{
    bool operator()(const pair<string, int>& p1, const pair<string, int>& p2)
    {
        return p1.second > p2.second;
    }
};
//单词分割
void WordsSlice(string& sentence, vector<string>& words)
{
    sentence[0] = tolower(sentence[0]);
    size_t beginPos = 0, endPos = 0;
    while(endPos != string::npos)
    {
        endPos = sentence.find(' ', beginPos);
        if(endPos != string::npos)
        {
            words.push_back(sentence.substr(beginPos, endPos - beginPos));
            beginPos = ++endPos;
        }
    }
    endPos = sentence.find('.', beginPos);
    words.push_back(sentence.substr(beginPos, endPos - beginPos));
}
//单词计数和排序
vector<pair<string, int>> WordsCountAndSort(vector<string>& words, map<string, int>& countMap)
{
    for(const auto& word : words) {
        countMap[word]++;
    }
    vector<pair<string, int>> countV(countMap.begin(), countMap.end());
    stable_sort(countV.begin(), countV.end(), Greater());
    return countV;
}

void ResOutput(const vector<pair<string, int>>& countV)
{
    for(const auto& e : countV) {
        cout << e.first << ':' << e.second << endl;
    }
}

int main()
{
    string sentence;
    getline(cin, sentence); //输入句子
    vector<string> words;
    WordsSlice(sentence, words); //分割单词
    map<string, int> countMap;
    vector<pair<string, int>> countV = WordsCountAndSort(words, countMap); //单词计数和排序
    ResOutput(countV); //结果输出
    return 0;
}