###### tags: `Week_1`, `String`

# String

## [205. Isomorphic Strings](https://leetcode.com/problems/isomorphic-strings)
harry:

# @param {String} s
# @param {String} t
# @return {Boolean}
def is_isomorphic(s, t)
    lookup = {}
    dict = Set.new
    s.size.times do |i|
        c = lookup[s[i]]
        if c.nil?
            if dict.include?(t[i]) # s[i] not seen, but t[i] already seen
                return false
            else 
              lookup[s[i]] = t[i]
              dict.add(t[i])
            end
        elsif c!=t[i]
            return false 
        end
    end
    true
end

Sam:

class Solution:
    def isIsomorphic(self, s: str, t: str) -> bool:
        
        dict_s = dict()
        s_list = []
        dict_t = dict()
        t_list = []
        
        for i in range(len(s)):
            if s[i] not in dict_s:
                dict_s[s[i]] = [i]
            else:
                dict_s[s[i]].append(i)
                
            if t[i] not in dict_t:
                dict_t[t[i]] = [i]
            else:
                dict_t[t[i]].append(i)
        
        for _, ar in dict_s.items():
            s_list.append(ar)
        for _, ar in dict_t.items():
            t_list.append(ar)
        
        return s_list == t_list

beny:

public bool IsIsomorphic(string s, string t)
        {
            HashSet<char> tHashSet = new HashSet<char>();
            Dictionary<char,char> sDictionary = new Dictionary<char, char>();
            
            for (int i = 0; i < s.Length; i++)
            {
                if (sDictionary.ContainsKey(s[i]))
                {
                    if (sDictionary[s[i]] != t[i]) {
                        return false;
                    } 
                }
                else
                {
                    if (!tHashSet.Contains(t[i]))
                    {
                        sDictionary.Add(s[i], t[i]);
                        tHashSet.Add(t[i]);
                    }
                    else { 
                        return false; 
                    }
                }
            }
            return true;
        }

## [392. Is Subsequence](https://leetcode.com/problems/is-subsequence)
harry:

# @param {String} s
# @param {String} t
# @return {Boolean}
def is_subsequence(s, t)
  checker = 0
  s.each_char do |c|
      while c != t[checker]
        return false if checker >= t.size - 1
        checker += 1
      end
      checker += 1
  end

  true
end

harry(2nd try):

# @param {String} s
# @param {String} t
# @return {Boolean}
def is_subsequence(s, t)
  return true if s == ""

  p_s = 0
  p_t = 0

  while p_t < t.size && p_s < s.size
    if s[p_s] == t[p_t]
      p_s += 1 
    end
    p_t += 1
  end

  p_s > s.size - 1
end

Sam:

class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        match_index = 0
        i = 0
        
        if len(t) < len(s):
            return False
        
        if len(s) == 0:
            return True
        
        while match_index < len(s) and i < len(t):
            if s[match_index] == t[i]:
                match_index += 1
            i += 1
            if match_index == len(s):
                return True

        return False

beny:

public bool IsSubsequence(string s, string t) {        
    if(s.Length > t.Length){
        return false;
    }
    int next = 0;
    for (int j = 0; j < s.Length; j++){
        if (next == t.Length) {
            return false;
        }
        for (int i = next; i < t.Length; i++)
        {
            next = i + 1;
            if (s[j] == t[i])
            {                        
                break;
            }else if(next== t.Length){
                return false;
            }                    
        }
    }
    return true;
}

beny(2nd try):

public class Solution {
    public bool IsSubsequence(string s, string t) {       

        if(s.Length == 0)
        {
            return true;
        }
        else if(s.Length > t.Length)
        {
            return false;
        }

        int index = 0;
        for(int i = 0;i < t.Length; i++)
        {
            if(s[index] == t[i]){
                index ++;
            }
            if(index == s.Length){
                return true;
            }
        }

        return false;
    }
}

## [290. Word Pattern](https://leetcode.com/problems/word-pattern/description/)
beny:

public class Solution {
    public bool WordPattern(string pattern, string s) {
        Dictionary<Char,string> dic = new Dictionary<Char,string>();
        string[] array = s.Split(' ');

        if(array.Length != pattern.Length)
        {
            return false;
        }

        for(int i = 0; i < pattern.Length; i ++)
        {
            if(dic.ContainsKey(pattern[i]))
            {
                if(array[i] != dic[pattern[i]])
                {
                    return false;
                }
            }
            else
            {
                if(!dic.ContainsValue(array[i]))
                {
                    dic.Add(pattern[i],array[i]);
                }
                else
                {
                    return false;
                }
            }
        }       

        return true;
    }
}