O(n) time and O(1) space easy to understand Java solution, 14ms


  • 0
    W

    The first string is the longest common prefix so far. The variable endIdx keeps track of the maximum index to be compared. The while loop finds the first index of a non-common character up to endIdx exclusive.

    public class Solution {
        public String longestCommonPrefix(String[] strs) {
            int len = strs.length;
            if (len == 0) return "";
            
            String prefix = strs[0];
            int endIdx = prefix.length();
            for (int i = 1; i < strs.length; i++) {
                String str = strs[i];
                int ptr = 0;
                while (ptr < endIdx && ptr < str.length() && prefix.charAt(ptr) == str.charAt(ptr)) ptr++;
                endIdx = ptr;
            }
            return prefix.substring(0, endIdx);
        }
    }
    

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