14. 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: strs = ["flower","flow","flight"]
Output: "fl"

Example 2:

Input: strs = ["dog","racecar","car"]
Output: ""
Explanation: There is no common prefix among the input strings.

Constraints:

• 1 <= strs.length <= 200
• 0 <= strs[i].length <= 200
• strs[i] consists of only lowercase English letters if it is non-empty.

Approach 01: Horizontal Scanning

class Solution {
public:
    string longestCommonPrefix(vector& strs) {
        if (strs.empty()) return "";
        string prefix = strs[0];
        for (int i = 1; i < strs.size(); i++) {
            while (strs[i].find(prefix) != 0) {
                prefix = prefix.substr(0, prefix.length() - 1);
                if (prefix.empty()) return "";
            }
        }
        return prefix;
    }
};

class Solution:
    def longestCommonPrefix(self, strs: List[str]) -> str:
        if not strs: return ""
        prefix = strs[0]
        for i in range(1, len(strs)):
            while not strs[i].startswith(prefix):
                prefix = prefix[:-1]
                if not prefix: return ""
        return prefix

class Solution {
    public String longestCommonPrefix(String[] strs) {
        if (strs.length == 0) return "";
        String prefix = strs[0];
        for (int i = 1; i < strs.length; i++) {
            while (strs[i].indexOf(prefix) != 0) {
                prefix = prefix.substring(0, prefix.length() - 1);
                if (prefix.isEmpty()) return "";
            }
        }
        return prefix;
    }
}