JumpGame-II.java

/* https://leetcode.com/problems/jump-game-ii/description/ */

/*
45. Jump Game II

You are given a 0-indexed array of integers nums of length n. You are initially positioned at nums[0].
Each element nums[i] represents the maximum length of a forward jump from index i. In other words, if you are at nums[i], you can jump to any nums[i + j] where:

0 <= j <= nums[i] and i + j < n
Return the minimum number of jumps to reach nums[n - 1]. The test cases are generated such that you can reach nums[n - 1].

 
Example 1:
Input: nums = [2,3,1,1,4]
Output: 2
Explanation: The minimum number of jumps to reach the last index is 2. Jump 1 step from index 0 to 1, then 3 steps to the last index.

Example 2:
Input: nums = [2,3,0,1,4]
Output: 2
 
Constraints:
1 <= nums.length <= 104
0 <= nums[i] <= 1000
*/

class JumpGame2 {
    public int jump(int[] nums) {
        int len = nums.length - 1, curr = -1, next = 0, ans = 0;
        for (int i = 0; next < len; i++) {
            if (i > curr) {
                ans++;
                curr = next;
            };
            next = Math.max(next, nums[i] + i);
        };
        return ans;
    }
}