19.1.26 [LeetCode14] 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.

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        if (strs.size() == 0)return "";
        int ans = 0, l = strs[0].length();
        for (int i =0; i < l; i++) {
            char c = strs[0][i];
            for (int j = 1; j < strs.size(); j++)
                if (strs[j][i] != c)
                    return strs[0].substr(0,ans);
            ans++;
        }
        return strs[0].substr(0, ans);
    }
};

唯一需要注意的地方是数组可能为空