45. Jump Game II

Medium

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

解題

func jump(nums []int) int {
    dp := make([]int, len(nums))
    dp[len(nums) - 1] = 0
    
    for i := len(nums) - 2; i >= 0; i-- {
        res := len(nums)
        for j := 1; j <= nums[i]; j++ {
            curIdx := i+j
            if curIdx < len(nums) && 1 + dp[curIdx] < res{
                res = 1+dp[curIdx]
            }
        }
        
        dp[i] = res
    }
    
    return dp[0]
}