记录一道贪心算法的题目 -----重构字符串

#include <map>
#include <string>
#include <queue>
#include <iostream>
#include <vector>

using namespace std;
// 自定义优先级队列排序规则
class mycomparison
{
bool reverse;
public:
  mycomparison(const bool& revparam=false)
    {reverse=revparam;}
  bool operator() (pair<char, int>& lhs, pair<char,int>&rhs) const
  {
    if (reverse) return (lhs.second > rhs.second);
    else return (lhs.second < rhs.second);
  }
};



class Solution {
public:
    string reorganizeString(string S) 
    {
        map<char, int> my_map;
        pair<char, int> temp1, temp2;
        string s = "";
        // 查找字符串次数
        int length = S.size();
        for(int i = 0; i < length; i++)
        {
            my_map[S[i]]++;
        }
        // 放入最大堆
        priority_queue<pair<char, int>,vector<pair<char,int>> ,mycomparison> max_heap;
        map<char, int>::iterator begin = my_map.begin();
        for(begin; begin != my_map.end(); begin++)
        {
            max_heap.push(*(begin)); 
        }
　　      // 弹出两个元素
        while(max_heap.size() > 1)
        {
            temp1 = max_heap.top();
            max_heap.pop();
            temp2 = max_heap.top();
            max_heap.pop();
            s = s + temp1.first + temp2.first;
            if(temp1.second >= 2)
            {
                //减1放回去
                temp1.second -= 1;
                max_heap.push(temp1);
            }
            if(temp2.second >= 2)
            {
                //减1放回去,重新调整顺序，优先级队列，好爽^-^
                temp2.second -= 1;
                max_heap.push(temp2);
            }
        }
        if (max_heap.size() == 1)
        {
          if (max_heap.top().second == 1)
          {
                s = s + max_heap.top().first;
          }
            else
            {
                s = "";
            }
        }
        return s;
    }
};