跳跃游戏 V

/*
 * Problem: Given an integer array arr and an integer d, you can jump from index i to:
 *    i + x where i + x < arr.length and 0 < x <= d
 *    i - x where i - x >= 0 and 0 < x <= d
 * You can only jump to index j if arr[i] > arr[j] and arr[i] > arr[k] for all k between i and j.
 * Return the maximum number of indices you can visit.
 * This solution uses Java Stream to sort indices and find the maximum jumps.
 */

import java.util.stream.IntStream;

public class Solution {
    public int maxJumps(int[] arr, int d) {
        int n = arr.length;
        int[] dp = new int[n];
        return IntStream.range(0, n)
                         .map(i -> dfs(arr, dp, i, d))
                         .max()
                         .orElse(1);
    }

    private int dfs(int[] arr, int[] dp, int i, int d) {
        if (dp[i] != 0) return dp[i];
        int max = 1;
        for (int j = 1; j <= d; j++) {
            if (i + j < arr.length && arr[i] > arr[i + j]) {
                max = Math.max(max, 1 + dfs(arr, dp, i + j, d));
            } else break;
        }
        for (int j = 1; j <= d; j++) {
            if (i - j >= 0 && arr[i] > arr[i - j]) {
                max = Math.max(max, 1 + dfs(arr, dp, i - j, d));
            } else break;
        }
        return dp[i] = max;
    }
}