leetcode[76]Minimum Window Substring

class Solution {
public:
/*
string minWindow(string S, string T) 
{
    string res="";
    if(S.empty()||T.empty()||S.size()<T.size())return res;
    int countNeed[256]={0};
    int countHas[256]={0};
    int countT=T.size();
    for (int i=0;i<countT;i++)
    {
        countNeed[T[i]]++;
        countHas[T[i]]++;
    }
    int start=0;
    int minSize=INT_MAX;
    for (int end=0;end<S.size();end++)
    {
        if (countHas[S[end]]>0)
        {
            countNeed[S[end]]--;
            if(countNeed[S[end]]>=0)countT--;
        }
        if (countT==0)
        {
            while(start<S.size())
            {
                if (countHas[S[start]]>0)
                {
                    if (countNeed[S[start]]<0)
                    {
                        countNeed[S[start]]++;
                        start++;
                    }
                    else  break;
                }
                else  start++;
            }
            if (end-start+1<=minSize)
            {
                minSize=end-start+1;
                res=S.substr(start,minSize);
            }
        }
    }
    return res;
}
*/

string minWindow(string S, string T) 
{
    string res="";
    if(S.empty()||T.empty()||S.size()<T.size())return res;
    int countT=T.size();
    map<char,int> MapNeed;
    for (int i=0;i<countT;i++)
    {
        MapNeed[T[i]]=0;
    }
    for (int i=0;i<countT;i++)
    {
        MapNeed[T[i]]++;
    }
    int start=0;
    int minSize=INT_MAX;
    for (int end=0;end<S.size();end++)
    {
        if (MapNeed.find(S[end])!=MapNeed.end())
        {
            MapNeed[S[end]]--;
            if (MapNeed[S[end]]>=0)countT--;
        }
        if (countT==0)
        {
            while (start<S.size())
            {
                if (MapNeed.find(S[start])!=MapNeed.end())
                {
                    if (MapNeed[S[start]]<0)
                    {
                        MapNeed[S[start]]++;
                        start++;
                    } 
                    else
                    {
                        break;
                    }
                }
                else  
                {
                    start++;
                }
            }
            if (end-start+1<=minSize)
            {
                minSize=end-start+1;
                res=S.substr(start, minSize);
            }
        }
    }
    return res;
}

};