Leetcode-14-最长公共前缀

1.我的暴力解法:

class Solution {
    public static int shortestLen=0;
    public String longestCommonPrefix(String[] strs) {
        int min_length=getShortestStr(strs);
        String res="";
 

        int i=0,j=1;

        for (;i<min_length;i++){
            char ch=strs[0].charAt(i);
            boolean flag=true;
            j=1;
            if(min_length==1){
                
                for (;j<strs.length;j++){
                    if(strs[j].charAt(0)!=strs[0].charAt(0)){
                        return "";
                    }
                }
                return ""+strs[0].charAt(0);
            }
            else{
                for (;j<strs.length;++j){
                    if(ch!=strs[j].charAt(i)){
                        
                        return res;
                    }
                }
                if(flag==true){
                    res+=(ch);
                }
            }
            
        }
        return res;
    }
    public int getShortestStr(String[] str){
        int res=999;
        if(str==null){
            return -1;
        }
        int i=0;
        while(i<str.length){
            if(str[i].length()<res){
                res=str[i].length();
            }
            i++;
        }
        return res;
    }
    
}

2.大佬解法

直接字符串排序,假设strs长度为n,则时间需要O(max(nlogn),shortest_str_len),一般也就是nlogn水平
CPP解法

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        if(strs.empty())
             return string();
        sort(strs.begin(), strs.end());
        string st = strs.front(), en = strs.back();
        int i, num = st.size();
        for(i = 0; i < num && st[i] == en[i]; i ++)
            ;
        return string(st, 0, i);
    }
};