MinimumCostForTickets.java

class MinimumCostForTickets {
    public int mincostTickets(int[] days, int[] costs) {
        int maxDays = days[days.length - 1];
        int[] dp = new int[maxDays + 1];
        int index = 0;
        for (int d = 1; d <= maxDays; d++) {
            dp[d] = dp[d - 1];
            if (d == days[index]) {
                int oneDayPass = dp[d - 1] + costs[0];
                int sevenDayPass = dp[Math.max(0, d - 7)] + costs[1];
                int thirtyDayPass = dp[Math.max(0, d - 30)] + costs[2];
                dp[d] = Math.min(oneDayPass, Math.min(sevenDayPass, thirtyDayPass));
                index++;
            }
        }
        return dp[maxDays];
    }
}