added problem 983

Author: SHA65536

problems/problem0983/min_cost_tickets.go

@@ -0,0 +1,62 @@
+package problem0983
+
+/*
+You have planned some train traveling one year in advance.
+The days of the year in which you will travel are given as an integer array days.
+Each day is an integer from 1 to 365.
+Train tickets are sold in three different ways:
+    a 1-day pass is sold for costs[0] dollars,
+    a 7-day pass is sold for costs[1] dollars, and
+    a 30-day pass is sold for costs[2] dollars.
+The passes allow that many days of consecutive travel.
+    For example, if we get a 7-day pass on day 2, then we can travel for 7 days: 2, 3, 4, 5, 6, 7, and 8.
+Return the minimum number of dollars you need to travel every day in the given list of days.
+*/
+
+func mincostTickets(days []int, costs []int) int {
+	// cache stores the costs for the last 30 days of travel
+	var cache [30]int
+	// travel[i] tells us if we travel on the ith day
+	var travel = make(map[int]struct{}, len(days))
+	var l = len(days) - 1
+	for _, d := range days {
+		travel[d] = struct{}{}
+	}
+
+	// Loop over all calendar days (not the given days)
+	for i := 1; i <= 365; i++ {
+		if _, ok := travel[i]; !ok {
+			// If we don't travel this day, take the last day cost
+			cache[i%30] = cache[(i-1)%30]
+		} else {
+			cache[i%30] = min(
+				cache[(i-1)%30]+costs[0],        // 1 day ticket
+				cache[max(0, i-7)%30]+costs[1],  // 7 day ticket
+				cache[max(0, i-30)%30]+costs[2], // 30 day ticket
+			)
+
+		}
+	}
+
+	return cache[days[l]%30]
+}
+
+func min(nums ...int) int {
+	min := nums[0]
+	for _, num := range nums {
+		if num < min {
+			min = num
+		}
+	}
+	return min
+}
+
+func max(nums ...int) int {
+	max := nums[0]
+	for _, num := range nums {
+		if num > max {
+			max = num
+		}
+	}
+	return max
+}

problems/problem0983/min_cost_tickets_test.go

@@ -0,0 +1,30 @@
+package problem0983
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type Result struct {
+	Days     []int
+	Costs    []int
+	Expected int
+}
+
+var Results = []Result{
+	{[]int{1, 4, 6, 7, 8, 20}, []int{2, 7, 15}, 11},
+	{[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 30, 31}, []int{2, 7, 15}, 17},
+	{[]int{1, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 21, 24, 25, 27, 28, 29, 30, 31, 34, 37, 38, 39, 41, 43, 44, 45, 47, 48, 49, 54, 57, 60, 62, 63, 66, 69, 70, 72, 74, 76, 78, 80, 81, 82, 83, 84, 85, 88, 89, 91, 93, 94, 97, 99}, []int{9, 38, 134}, 423},
+}
+
+func TestMinCostOfTickets(t *testing.T) {
+	assert := assert.New(t)
+
+	for _, res := range Results {
+		want := res.Expected
+		got := mincostTickets(res.Days, res.Costs)
+		assert.Equal(want, got, fmt.Sprintf("%+v", res))
+	}
+}

readme.md

@@ -305,6 +305,7 @@ Each problem is in it's own directory, with test files. There are helper package
 | 0977 | [Squares of a Sorted Array](https://leetcode.com/problems/squares-of-a-sorted-array) | [My Solution](./problems/problem0977) | ✅ |
 | 0980 | [Unique Paths III](https://leetcode.com/problems/unique-paths-iii) | [My Solution](./problems/problem0980) | ✅ |
 | 0981 | [Time Based Key-Value Store](https://leetcode.com/problems/time-based-key-value-store) | [My Solution](./problems/problem0981) | ✅ |
+| 0983 | [Minimum Cost For Tickets](https://leetcode.com/problems/minimum-cost-for-tickets) | [My Solution](./problems/problem0983) | ✅ |
 | 0985 | [Sum of Even Numbers After Queries](https://leetcode.com/problems/sum-of-even-numbers-after-queries) | [My Solution](./problems/problem0985) | ✅ |
 | 0987 | [Vertical Order Traversal of a Binary Tree](https://leetcode.com/problems/vertical-order-traversal-of-a-binary-tree) | [My Solution](./problems/problem0987) | ✅ |
 | 0989 | [Add to Array-Form of Integer](https://leetcode.com/problems/add-to-array-form-of-integer) | [My Solution](./problems/problem0989) | ✅ |