_14.java

package com.fishercoder.solutions;

/**
 * 14. Longest Common Prefix
 *
 * Write a function to find the longest common prefix string amongst an array of strings.
 */

public class _14 {

    public static class Solution1 {
        public String longestCommonPrefix(String[] strs) {
            if (strs.length == 0) {
                return "";
            }

            int i = 0;
            String prefix = "";
            String result;
            boolean broken = false;
            while (true) {
                i++;
                result = prefix;
                if (i > strs[0].length()) {
                    break;//this will break out the while loop
                }
                prefix = strs[0].substring(0, i);
                for (String word : strs) {
                    if (i > word.length() || !word.startsWith(prefix)) {
                        broken = true;
                        break;//this will only break out of the for loop
                    }
                }
                if (broken) {
                    break;//this will break out the while loop
                }
            }
            return result;
        }
    }

    public static class Solution2 {
        //horizontal scan
        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;
        }
    }

    public static class Solution3 {
        //vertical scan
        public String longestCommonPrefix(String[] strs) {
            if (strs.length == 0) {
                return "";
            }
            for (int i = 0; i < strs[0].length(); i++) {
                char c = strs[0].charAt(i);
                for (int j = 1; j < strs.length; j++) {
                    if (i == strs[j].length() || strs[j].charAt(i) != c) {
                        return strs[0].substring(0, i);
                    }
                }
            }
            return strs[0];
        }
    }
}