FrogJump.java

// Source : https://leetcode-cn.com/problems/frog-jump/
// Author : cornprincess
// Date   : 2021-04-29

/***************************************************************************************************** 
 *
 * 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
 ******************************************************************************************************/