Package g0401_0500.s0403_frog_jump

Class Solution

  • public class Solution
extends Object
    403 - Frog Jump.

    Hard

    A frog is crossing a river. The river is divided into some number of units, and at each unit, there may or may not exist a stone. The frog can jump on a stone, but it must not jump into the water.

    Given a list of stones’ positions (in units) in sorted ascending order , determine if the frog can cross the river by landing on the last stone. Initially, the frog is on the first stone and assumes the first jump must be 1 unit.

    If the frog’s last jump was k units, its next jump must be either k - 1, k, or k + 1 units. The frog can only jump in the forward direction.

    Example 1:

    Input: stones = [0,1,3,5,6,8,12,17]

    Output: true

    Explanation: The frog can jump to the last stone by jumping 1 unit to the 2nd stone, then 2 units to the 3rd stone, then 2 units to the 4th stone, then 3 units to the 6th stone, 4 units to the 7th stone, and 5 units to the 8th stone.

    Example 2:

    Input: stones = [0,1,2,3,4,8,9,11]

    Output: false

    Explanation: There is no way to jump to the last stone as the gap between the 5th and 6th stone is too large.

    Constraints:

    • 2 <= stones.length <= 2000
    • 0 <= stones[i] <= 231 - 1
    • stones[0] == 0
    • stones is sorted in a strictly increasing order.

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • canCross

        public boolean canCross​(int[] stones)