leetcode 93: Restore IP Addresses

最新推荐文章于 2025-05-26 21:34:34 发布

mikefan1991

最新推荐文章于 2025-05-26 21:34:34 发布

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class Solution {
public:
    vector<string> restoreIpAddresses(string s) {
        vector<string> res;
        helper(s,0,3,res);
        return res;
    }
    void helper(string s, int start, int dot, vector<string>& res)
    {
        if(!dot)//no more dots need to be added
        {
            if(s.size()-start==2&&s[start]=='0')//the last part is less than 10
                return;
            if(s.size()-start==3)
            {
                int num=(s[start]-'0')*100+(s[start+1]-'0')*10+s[start+2]-'0';
                if(num<100||num>255)
                    return;
            }
            res.push_back(s);
        }
        for(int l=0;l<3&&start+l<s.size()-1;l++)
        {
            double ave=(double)(s.length()-start-l-1)/dot;
            if(ave>3)//if the remaining string cannot be divided by dots
                continue;
            if(l==1)
            {
                int num=(s[start]-'0')*10+s[start+1]-'0';
                if(num<10)
                    return;
            }
            else if(l==2)
            {
                int num=(s[start]-'0')*100+(s[start+1]-'0')*10+s[start+2]-'0';
                if(num>255||num<100)
                    return;
            }
            string temp;
            temp+=s.substr(0,start+l+1);
            temp+='.';
            temp+=s.substr(start+l+1);
            helper(temp,start+l+2,dot-1,res);
        }
    }
};