1-6 lines, O(n) time, O(1) space

  • 16

    Solution 1

    Going forwards. m tells the maximum index we can reach so far.

    def canJump(self, nums):
        m = 0
        for i, n in enumerate(nums):
            if i > m:
                return False
            m = max(m, i+n)
        return True

    Solution 2

    One-liner version:

    def canJump(self, nums):
        return reduce(lambda m, (i, n): max(m, i+n) * (i <= m), enumerate(nums, 1), 1) > 0

    Solution 3

    Going backwards, most people seem to do that, here's my version.

    def canJump(self, nums):
        goal = len(nums) - 1
        for i in range(len(nums))[::-1]:
            if i + nums[i] >= goal:
                goal = i
        return not goal

    Solution 4

    C version.

    bool canJump(int* nums, int n) {
        int goal=n-1, i;
        for (i=n; i--;)
            if (i+nums[i] >= goal)
        return !goal;

  • 0

    Good solutions,Thanks for your share. But it seems some of these are not time-saving ones.

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