贪心法求解

class Solution {
public:
    /**
     * 
     * @param strs string字符串vector 
     * @return string字符串
     */
    string longestCommonPrefix(vector<string>& strs) {
        // write code here
        if(!strs.size()) return "";

        sort(strs.begin(),strs.end()); //按照字典序排序得到所有子串顺序

        string a = strs.front(), b = strs.back();
        int i;
        for(i = 0;i<a.size()&&a[i]==b[i];i++);

        return a.substr(0,i);
    }
};