[LeetCode] Longest Common Prefix

Write a function to find the longest common prefix string amongst an array of strings.

思路：

这道题其实很简单，但是比较别扭的是这道题不是一般情况下的按层来遍历，而是按列来遍历。可以考虑用第一个string做外层loop，需要注意的是各个string的长短不一样，所以inner loop务必check index。

注意：

break只能break一层loop

class Solution {
    public String longestCommonPrefix(String[] strs) {
        if (strs == null || strs.length == 0) return "";
        if (strs.length == 1) return strs[0];
        int i = 0, j = 0;
        for (i = 0; i < strs[0].length(); i++) {
            char c = strs[0].charAt(i);
            for (j = 0; j < strs.length; j++) {
                if (i >= strs[j].length() || strs[j].charAt(i) != c) 
                    return strs[0].substring(0, i);
            }
        }
        return strs[0];
    }
}

 python version

找到最短的str这个写法很实用

class Solution:
    def longestCommonPrefix(self, strs: List[str]) -> str:
        if strs is None or len(strs) == 0:
            return ''       
        
        shortest = min(strs, key=len)
        for i, ch in enumerate(shortest):
            for a_str in strs:
                if a_str[i] != ch:
                    return shortest[:i]
        
        return shortest