Leetcode: Jump Game II @Python

class Solution:
    # @param A, a list of integers
    # @return an integer
    def jump(self, A):
        n=len(A)
        reach=0
        if n<=1: return 0
        jumpNum=0
        while True:
            jumpNum+=1
            for i in range(reach+1):
                reach=max(reach, i+A[i])
            if reach>=n-1:
                return jumpNum