字符串最长无重复字串[c++]

class Solution {
public:

int maxLength(vector<int>& arr) {
    // write code here

    map<int,int> mpTemp;
    int maxLength = 0;
    int start=0;
    for(int j=0;j<arr.size();j++){
        if(mpTemp.count(arr[j])==0){
            mpTemp[arr[j]]=j;
            if(j==arr.size()-1)//若数组最后一位元素之前没出现过
                maxLength =std::max(j-start+1,maxLength);
        }
        else{
            maxLength =std::max(j-start,maxLength);
            start=std::max(mpTemp[arr[j]]+1, start);  //这一步想了好久
            mpTemp[arr[j]]=j;
        }
    }
    return maxLength;
}

};