see-14. Longest Common Prefix

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
    	string ans; 
        if(strs.size()==0)
            return ans;

	    int minLen=INT_MAX;
	    for(auto item:strs)
	    	minLen=min(minLen,item.size());  //计算最短字符串的长度

	    for(int i=0;i<minLen;i++)
	    {
	    	int num=0;
	    	for(auto item:strs)
	    	{
	    		if(item[i]==strs[0][i])
	    			num++;
	    		else
	    			break;
	    	}
	    	if(num==strs.size())
	    		ans = ans + strs[0][i];
	    	else
	    		break;
	    }

	    return ans;      
    }
    int min(int a,int b)
    {
        return a<b?a:b;
    }
};