Jump Game — Python

# Time:  O(n)
# Space: O(1)

class Solution(object):
    # @param A, a list of integers
    # @return a boolean
    def canJump(self, A):
        reachable = 0
        for i, length in enumerate(A):
            if i > reachable:
                break
            reachable = max(reachable, i + length)
        return reachable >= len(A) - 1