14. Longest Common Prefix

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

For instance: ["ab", "bc"] returns ""; ["a", "ab"] returns "a".

public class Solution {
    public String longestCommonPrefix(String[] strs) {
        if (strs == null || strs.length == 0) return "";
        if (strs.length == 1) return strs[0];
        
        StringBuilder sb = new StringBuilder();

        for (int j = 0; j < strs[0].length(); j++) {
            for (int i = 0; i < strs.length; i++) {
                if (strs[i].length() < j + 1 || strs[i].charAt(j) != strs[0].charAt(j)) {
                    return sb.toString();
                }
            }
            sb.append(strs[0].charAt(j));
        }
        return sb.toString();
    }
}

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