Build the table . Note that the lower diagonal values of table are useless and not filled in the process . The values are filled in a manner similar to Matrix Chain Multiplication DP solution ( Seewww . geeksforgeeks . org / matrix - chain - multiplication - dp - 8 / ) . cl is length of https : substring
for ( cl = 2 ; cl <= n ; cl ++ ) { for ( i = 0 ; i < n - cl + 1 ; i ++ ) { j = i + cl - 1 ; if ( str [ i ] == str [ j ] && cl == 2 ) L [ i ] [ j ] = 2 ; else if ( str [ i ] == str [ j ] ) L [ i ] [ j ] = L [ i + 1 ] [ j - 1 ] + 2 ; else L [ i ] [ j ] = max ( L [ i ] [ j - 1 ] , L [ i + 1 ] [ j ] ) ; } } return L [ 0 ] [ n - 1 ] ; }