Longest Common Prefix

Description：

Write a function to find the longest common prefix string amongst an array of strings.（最长公共字串）

Code：

string merge(string&str1, string&str2)
{
string result="";
int n = (str1.size()<=str2.size())?str1.size():str2.size();
for (int i = 0; i < n; ++i)
{
if (str1[i]==str2[i])
result=result+str1[i];
else
return result;
}
return result;
}
string longestCommonPrefix(vector<string>& strs, int start, int end)
{
if (start < end)
{
int middle = (start+end)/2;
string str1 = longestCommonPrefix(strs, start, middle);
if (str1=="")
return str1;
string str2 = longestCommonPrefix(strs, middle+1, end);
if (str2=="")
return str2;
return merge(str1, str2);
}
else
return strs[start];
}
string longestCommonPrefix(vector<string>& strs) {
if (strs.size()==0)
return "";
return longestCommonPrefix(strs,0,strs.size()-1);
}