LeetCode # Longest Common Prefix #

"""
Programmer  :   EOF
Date        :   2015.04.15
File        :   lcp.py
E-mail      :   jasonleaster@gmail.com
"""

"""
Varible Description:
    @ret_string :   We store the string to be returned into this varible
    @length     :   Find the min length of the inputed string in the list

"""

class Solution:
    def longestCommonPrefix(self, strs):
        ret_string = ""

        if len(strs) == 0:
            return ret_string
        else:
            length = len(strs[0])

        for i in range(0, len(strs)):
            if length > len(strs[i]):
                length = len(strs[i])

        if len(strs) != 1:
            for j in range(0, length):
                """
                    We check the element from back to front.
                    If we can't get the first string in the 
                    inputed list of string, we can tell that 
                    we the comman prefix break there.
                """
                i = len(strs) - 1
                while i >= 1:
                    if strs[i][j] != strs[i-1][j] :
                        break
                    i -= 1

                if i == 0:
                    ret_string += strs[i][j]
                else:
                    break

        return ret_string

#-------- just for testing ----------

s = Solution()
strings = ["acb", "bca"]
print s.longestCommonPrefix(strings)

strings = ["a", "b"]
print s.longestCommonPrefix(strings)

strings = ["a"]
print s.longestCommonPrefix(strings)

strings = ["abcd", "ab", "abc"]
print s.longestCommonPrefix(strings)

package longest_substring_without_repeating_characters;

import java.util.HashMap;
import java.util.Map;

public class Solution {
	public int lengthOfLongestSubstring(String s) {
		int maxLen = 0;
		int start = 0;
		Map<Character, Integer> record = new HashMap<>(256);
		for (int i = 0; i < s.length(); i++) {
			char ch = s.charAt(i);
			Integer pos = record.get(ch);
			start = Math.max(start, pos == null ? 0 : pos + 1);
			maxLen = Math.max(i - start + 1, maxLen);
			record.put(ch, i);
		}
		return maxLen;
	}

	public static void main(String[] args) {
		System.out.println(new Solution().lengthOfLongestSubstring("wlrbbmqbhcdarzowkkyhiddqscdxrjmowfrxsjybldbefsarcbynecdyggxxpklorellnmpapqfwkhopkmco"));
	}
}

// Source : https://oj.leetcode.com/problems/longest-common-prefix/
// Author : Hao Chen
// Date   : 2014-07-03

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

#include <iostream>
#include <string>
#include <vector>
using namespace std;


string longestCommonPrefix(vector<string> &strs) {
    string word;
    if (strs.size()<=0) return word;
    for(int i=1; i<=strs[0].size(); i++){
        string w = strs[0].substr(0, i);
        bool match = true;
        int j=1;
        for(j=1; j<strs.size(); j++){
            if (i>strs[j].size() || w!=strs[j].substr(0, i) ) {
                match=false;
                break;
            }
        }
        if (!match) {
            return word;
        }
        word = w;
    }
    return word;
}

int main()
{
    const char* s[]={"abab","aba","abc"};
    vector<string> v(s, s+3);
    cout << longestCommonPrefix(v) <<endl;
}