Longest Palindromic Subsequence | DP | Returns the length of the longest palindromic subsequence in seq ; Base Case 1 : If there is only 1 character ; Base Case 2 : If there are only 2 characters and both are same ; If the first and last characters match ; If the first and last characters do not match ; Driver Code
< ? php function lps ( $ seq , $ i , $ j ) { if ( $ i == $ j ) return 1 ; if ( $ seq [ $ i ] == $ seq [ $ j ] && $ i + 1 == $ j ) return 2 ; if ( $ seq [ $ i ] == $ seq [ $ j ] ) return lps ( $ seq , $ i + 1 , $ j - 1 ) + 2 ; return max ( lps ( $ seq , $ i , $ j - 1 ) , lps ( $ seq , $ i + 1 , $ j ) ) ; } $ seq = " GEEKSFORGEEKS " ; $ n = strlen ( $ seq ) ; echo " The ▁ length ▁ of ▁ the ▁ LPS ▁ is ▁ " . lps ( $ seq , 0 , $ n - 1 ) ; ? >