Longest String Chain | Leetcode 1048 solution

 You are given an array of words where each word consists of lowercase English letters.

wordA is a predecessor of wordB if and only if we can insert exactly one letter anywhere in wordA without changing the order of the other characters to make it equal to wordB.

• For example, "abc" is a predecessor of "abac", while "cba" is not a predecessor of "bcad".

A word chain is a sequence of words [word1, word2, ..., wordk] with k >= 1, where word1 is a predecessor of word2, word2 is a predecessor of word3, and so on. A single word is trivially a word chain with k == 1.

Return the length of the longest possible word chain with words chosen from the given list of words.

 

Example 1:

Input: words = ["a","b","ba","bca","bda","bdca"]
Output: 4
Explanation: One of the longest word chains is ["a","ba","bda","bdca"].

Example 2:

Input: words = ["xbc","pcxbcf","xb","cxbc","pcxbc"]
Output: 5
Explanation: All the words can be put in a word chain ["xb", "xbc", "cxbc", "pcxbc", "pcxbcf"].

Example 3:

Input: words = ["abcd","dbqca"]
Output: 1
Explanation: The trivial word chain ["abcd"] is one of the longest word chains.
["abcd","dbqca"] is not a valid word chain because the ordering of the letters is changed.

 

Constraints:

• 1 <= words.length <= 1000
• 1 <= words[i].length <= 16
• words[i] only consists of lowercase English letters.

solution : 

class Solution { public:   static bool solve(string &a , string &b)   {       return a.length() < b.length();   }     bool compare(string &a , string &b )     {         if(a.length() < b.length())         {             return compare(b , a);         }         if(a.length() != b.length() +1)         {             return false;         }         int flag =0;         int j =0;         int size = a.size();         for(int i =0 ; i < size ;i++)         {             if(a[i] != b[j])             {                    if(flag ==1)                 {                     return false;                 }                 flag =1;                 continue;             }             else             {                 j++;             }         }         if( j == b.length())         {             return true;         }         return false;     }     int longestStrChain(vector<string>& words) {                   int cnt = INT_MIN;           sort(words.begin() , words.end(), solve);           int size = words.size();           vector<int>dp(size +1 , 1);           for(int i = 0; i < size ; i++)           {               for(int j = 0 ; j < i ; j++)               {                   if(compare(words[i], words[j]) )                   {                       dp[i] = max(dp[i], dp[j] +1);                   }               }               cnt = max(cnt , dp[i]);           }           return cnt;     } };