【LeetCode & 剑指offer刷题】字符串题10：Longest Common Prefix
【LeetCode & 剑指offer 刷题笔记】目录（持续更新中...）
Longest Common Prefix
Write a function to find the longest common prefix string amongst an array of strings.
If there is no common prefix, return an empty string "".
Example 1:
Input: ["flower","flow","flight"]
Output: "fl"
Example 2:
Input: ["dog","racecar","car"]
Output: ""
Explanation: There is no common prefix among the input strings.
Note:
All given inputs are in lowercase letters a-z.
//问题：各字符串最长公共前缀
/*
class Solution
{
public:
string longestCommonPrefix(vector<string>& strs)
{
if(strs.size() == 0) return ""; //返回空串
if(strs.size() == 1) return strs[0]; //返回自身
string res = strs[0]; //初始化
int length = res.size(); //公共前缀的长度
for(int i = 1; i<strs.size(); i++) //从第二个单词开始遍历
{
int temp = -1;
for(int j = 0; j<length && j<strs[i].size(); j++)//遍历单词内字符
{
if(strs[i][j] == res[j] ) temp = j; //保存当前索引
else break; //一旦不相等就退出循环
}
length = temp + 1;
}
res[length] = '\0'; //打上结束字符
return res;
}
};*/
//也可用string的成员函数substr简化程序
class Solution
{
public:
string longestCommonPrefix(vector<string>& strs)
{
if(strs.empty()) return ""; //返回空串
string prefix = strs[0];
for(int i = 1; i<strs.size(); i++)
{
for(int j = 0; j<prefix.size(); j++)
{
if(strs[i][j] != prefix[j])
{
prefix = prefix.substr(0, j); //公共前缀更新,substr中区间为前闭后开，故当遇到第一个不相等字符后，就将前面相等的字符复制过去，之后j<prefix.size()无法满足，退出循环。
}
}
}
return prefix;
}
};
