As Bob pointed out, ‘i’ should start from level, not 0. In fact, ‘i’ should only be equal to level – it should not increment until length. Consequently, Rakesh is also correct: the first ‘for’ loop is in fact, redundant. The code may be corrected completely by eliminating the ‘i’ for loop, and subsequently replacing ‘i’ by ‘level’ in the following 4 lines of code inside the ‘j’ for loop.