45 Jump Game II

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

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 < nReturn __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 	
It's guaranteed that you can reach nums[n - 1].

https://www.youtube.com/watch?v=dJ7sWiOoK7g

  • code
class Solution {
    public int jump(int[] nums) {
        int left = 0, right = 0, step = 0;
        while (right < nums.length - 1){
            int cur_far = 0;
            for (int i = left; i <= right; i++){
                cur_far = Math.max(cur_far, i + nums[i]);
            }
            left = right + 1;
            right = cur_far;
            step++;
        }
        return step;
    }
}