一、题目描述

二、算法原理

三、代码实现

代码实现1：我自己写的比较挫，但是比较简单。

class Solution {
public:int minNumberOfFrogs(string croakOfFrogs) {unordered_map<char,int> hash;hash['c']=0,hash['r']=0,hash['o']=0,hash['a']=0,hash['k']=0;for(int i=0;i<croakOfFrogs.size();i++){if(croakOfFrogs[i]=='c'){if(hash['k']==0)hash['c']++;else{hash['k']--;hash['c']++;}}else if(croakOfFrogs[i]=='r'){if(hash['c']!=0){hash['r']++;hash['c']--;}else{return -1;}}else if(croakOfFrogs[i]=='o'){if(hash['r']!=0){hash['o']++;hash['r']--;}else{return -1;}}else if(croakOfFrogs[i]=='a'){if(hash['o']!=0){hash['a']++;hash['o']--;}else{return -1;}}else if(croakOfFrogs[i]=='k'){if(hash['a']!=0){hash['k']++;hash['a']--;}else{return -1;}}}string str="croa";for(int i=0;i<str.size();i++){if(hash[str[i]]!=0){return -1;}}return hash['k'];}
};

代码实现2：大佬写的，干净简洁。

class Solution {
public:int minNumberOfFrogs(string croakOfFrogs) {string str="croak";int n=str.size();vector<int> hash(n);unordered_map<char,int> index;for(int i=0;i<n;i++){index[str[i]]=i;}for(auto ch:croakOfFrogs){if(ch=='c'){if(hash[n-1]!=0) hash[n-1]--;hash[0]++;}else{int i=index[ch];if(hash[i-1]==0){return -1;}else{hash[i-1]--;hash[i]++;}}}for(int i=0;i<n-1;i++){if(hash[i]!=0){return -1;}}return hash[n-1];}
};