45. Jump Game II

难度: Medium

题目描述

You are given a 0-indexed array of integers nums of length n. You are initially positioned at index 0.

Each element nums[i] represents the maximum length of a forward jump from index i. In other words, if you are at index i, you can jump to any index (i + j) where:

• 0 <= j <= nums[i] and
• i + j < n

Return the minimum number of jumps to reach index n - 1. The test cases are generated such that you can reach index 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].

解题思路

代码实现

解决方案

java

class Solution {
    public int jump(int[] nums) {
        int n = nums.length;
        if (n == 1) {
            return 0;
        }
        int jumps = 0;
        int currentMax = 0;
        int nextMax = 0;
        for (int i = 0; i < n; i++) {
            nextMax = Math.max(nextMax, i + nums[i]);
            if (i == currentMax) {
                jumps++;
                currentMax = nextMax;
                if (currentMax >= n - 1) {
                    break;
                }
            }
        }
        return jumps;
    }
}