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 . substring ( 0 , i ) , S2 . substring ( n - i , n ) ) && isScramble ( S1 . substring ( i , n ) , S2 . substring ( 0 , n - i ) ) ) { flag = true ; return true ; } }