LeetCode T45 Jump Game II

题目地址

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

题目描述

Given an array of non-negative integers nums, you are initially positioned at the first index of the array.

Each element in the array represents your maximum jump length at that position.

Your goal is to reach the last index in the minimum number of jumps.

You can assume that you can always reach the last index.

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 <= 3 * 10⁴
• 0 <= nums[i] <= 10⁵

思路

贪心，找到从当前步跳到的步数加起来最远的位置，直到终点。

题解

class Solution {
    public int jump(int[] nums) {
        if(nums.length==1) return 0;
        int max_pos = 0;
        int next = 0;
        int step=0;
        for(int i=0;i<nums.length;){
            step++;
            if(i+nums[i]>= nums.length-1) return step;
            max_pos = 0;
            for(int j=0;j<=nums[i];++j){
                if(j+nums[i+j]>max_pos){
                    max_pos = j+nums[i+j];
                    next = j;
                }
            }
            i += next;
        }
        return step;
    }
}