Check if S2 [ 0. . . i ] is a scrambled string of S1 [ n - i ... n ] and S2 [ i + 1. . . n ] is a scramble string of S1 [ 0. . . n - i - 1 ]
if ( isScramble ( S1 . substr ( 0 , i ) , S2 . substr ( n - i , i ) ) && isScramble ( S1 . substr ( i , n - i ) , S2 . substr ( 0 , n - i ) ) ) { return true ; } }