go: add «983. Minimum Cost For Tickets»

URL:	https://leetcode.com/problems/minimum-cost-for-tickets/
Signed-off-by: Matej Focko <me@mfocko.xyz>

go/minimum-cost-for-tickets.go

@@ -0,0 +1,25 @@
+package main
+
+func mincostTickets(days []int, costs []int) int {
+	daily, weekly, monthly := costs[0], costs[1], costs[2]
+
+	lastDay := days[len(days)-1]
+
+	dp := make([]int, lastDay+1)
+	for i, day := 0, 1; day <= lastDay; day++ {
+		if day < days[i] {
+			// skip tickets when not travelling
+			dp[day] = dp[day-1]
+			continue
+		}
+
+		dp[day] = min(
+			dp[day-1]+daily,
+			dp[max(0, day-7)]+weekly,
+			dp[max(0, day-30)]+monthly,
+		)
+		i++
+	}
+
+	return dp[lastDay]
+}