[LeetCode 题解]: Longest Common Prefix

 class Solution {
public:
string getPrefix(string a,string b)   // 辅助函数用于获取两个字符串的公共前缀
{
string ans;
for(int i=0;i<a.size() && i<b.size();i++)
{
if(a[i]==b[i])  ans+=a[i];
else break;
}
return ans;
}
string longestCommonPrefix(vector<string> &strs) {
string a;
int len = strs.size();
if(!len) return a;
a = strs[0];
for(int i=1;i<len;i++) a= getPrefix(a,strs[i]);
return a;
}
};

 class Solution {
public:
string getPrefix(string a,string b)   //辅助函数，用于获取两个字符串的公共前缀
{
string ans;
for(int i=0;i<a.size() && i<b.size();i++)
{
if(a[i]==b[i])  ans+=a[i];
else break;
}
return ans;
}
string commonPrefix(int left,int right, vector<string> &strs)   //分治法寻找commonPrefix
{
if(left>=right) return strs[left];
if(left+1==right) return getPrefix(strs[left],strs[right]);
int middle = (right+left)>>1;
return getPrefix(commonPrefix(left,middle,strs),commonPrefix(middle+1,right,strs));
}
string longestCommonPrefix(vector<string> &strs) {
int i=0,len=strs.size();
string a;
if(!len) return a;
return commonPrefix(0,len-1,strs);
}
};