Leetcode25: Longest Common Prefix

Write a function to find the longest common prefix string amongst an array of strings.

求若干字符串的最长公共前缀。

首先若无字符串，返回“”；接下来求得其中最短字符串的长度len，比较公共前缀只需最多比较len次；最后比较所有字符串里每一位上的字符。

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        if(strs.size() == 0)
            return "";
        //if(strs.size() == 1)
            //return strs[0];

        int len = strs[0].length();
        for(int i = 1; i < strs.size(); i++)
        {
            if(len > strs[i].length())
                len = strs[i].length();
        }

        if(len == 0)
            return "";

        int i = 0;
        int j = 1;
        bool a = true;
        while(i<len && a)
        {
            for(j = 1; j < strs.size(); j++)
            {
                if(strs[j][i] != strs[j-1][i])
                {
                    a = false;
                    break;
                }
            }
            if(j == strs.size())
            {
                i++;
            }
        }

        return strs[0].substr(0, i);
    }
};