LongestCommonPrefix.java

package com.examplehub.leetcode.easy;

/** https://leetcode.com/problems/longest-common-prefix/solution/ */
public class LongestCommonPrefix {
  public static String solution1(String[] strings) {
    if (strings == null || strings.length == 0) {
      return "";
    }
    if (strings.length == 1) {
      return strings[0];
    }
    String longestCommonPrefix = "";
    for (int i = 1; i <= strings[0].length(); i++) {
      String prefix = strings[0].substring(0, i);
      for (int j = 1; j < strings.length; j++) {
        if (strings[j].indexOf(prefix) != 0) {
          return longestCommonPrefix;
        }
        if (j == strings.length - 1) {
          longestCommonPrefix = prefix;
        }
      }
    }
    return longestCommonPrefix;
  }

  public static String solution2(String[] strings) {
    if (strings.length == 0) {
      return "";
    }
    String longestCommonPrefix = strings[0];
    for (int i = 1; i < strings.length; i++) {
      while (strings[i].indexOf(longestCommonPrefix) != 0) {
        longestCommonPrefix = longestCommonPrefix.substring(0, longestCommonPrefix.length() - 1);
        if (longestCommonPrefix.equals("")) {
          return "";
        }
      }
    }
    return longestCommonPrefix;
  }
}