403.Frog Jump === ###### tags: `Hard` `Array` `DP` [403. Frog Jump](https://leetcode.com/problems/frog-jump/) ### 題目描述 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. ### 範例 **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]` <= 2^31^ - 1 * `stones[0]` == 0 * `stones` is sorted in a strictly increasing order. ### 解答 ### Reference [回到題目列表](https://marsgoat.github.io/XNnote/coding/leetcodeEveryDay.html)