M15t

import java.util.HashSet;

class Solution {
    public int solution(int[] A) {
        int currentPosition = 0;
        int jumps = 0;
        HashSet<Integer> visited = new HashSet<>();

        while (currentPosition >= 0 && currentPosition < A.length) {
            if (visited.contains(currentPosition)) {

M15t

class Solution {
    public int solution(int[] A) {
        int[] dp = new int[31]; // dp[i] stores the minimum cost to travel up to day i
        int n = A.length;
        int travelIndex = 0; // pointer to the current travel date
        
        for (int i = 1; i <= 30; i++) {
            if (travelIndex < n && i == A[travelIndex]) { // if i is a travel date
                int oneDayCost = dp[i - 1] + 2; // cost if using a 1-day ticket on day i
                int sevenDayCost = i > 7 ? dp[i - 7] + 7 : 7; // cost if using a 7-day ticket on day i