added problem 1601

Author: SHA65536

problems/problem1601/max_transfers.go

@@ -0,0 +1,60 @@
+package problem1601
+
+/*
+We have n buildings numbered from 0 to n - 1. Each building has a number of employees.
+It's transfer season, and some employees want to change the building they reside in.
+You are given an array requests where requests[i] = [fromi, toi] represents an employee's request to transfer from building fromi to building toi.
+All buildings are full, so a list of requests is achievable only if for each building, the net change in employee transfers is zero.
+This means the number of employees leaving is equal to the number of employees moving in.
+For example if n = 3 and two employees are leaving building 0, one is leaving building 1, and one is leaving building 2,
+there should be two employees moving to building 0, one employee moving to building 1, and one employee moving to building 2.
+Return the maximum number of achievable requests.
+*/
+
+func maximumRequests(n int, reqs [][]int) int {
+	var res int
+	var diffs = make([]int, n)
+	calcRequests(reqs, diffs, 0, &res)
+	return res
+}
+
+func calcRequests(reqs [][]int, diffs []int, cur int, res *int) {
+	if len(reqs) == 0 {
+		// If we processed all the requests, check that there is no surplus
+		if allZeros(diffs) {
+			*res = max(*res, cur)
+		}
+		return
+	}
+
+	// Reject a request
+	// Find the max starting from the next request
+	calcRequests(reqs[1:], diffs, cur, res) // cur stays the same because we rejected
+
+	// Accept a request
+	diffs[reqs[0][0]]--
+	diffs[reqs[0][1]]++
+	// Find the max starting from the next request
+	calcRequests(reqs[1:], diffs, cur+1, res) // cur increases because we accepted
+
+	// Undo the request
+	diffs[reqs[0][0]]++
+	diffs[reqs[0][1]]--
+
+}
+
+func allZeros(inc []int) bool {
+	for i := range inc {
+		if inc[i] != 0 {
+			return false
+		}
+	}
+	return true
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}

problems/problem1601/max_transfers_test.go

@@ -0,0 +1,39 @@
+package problem1601
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type TestCase struct {
+	N        int
+	Requests [][]int
+	Expected int
+}
+
+var TestCases = []TestCase{
+	{5, [][]int{{0, 1}, {1, 0}, {0, 1}, {1, 2}, {2, 0}, {3, 4}}, 5},
+	{3, [][]int{{0, 0}, {1, 2}, {2, 1}}, 3},
+	{4, [][]int{{0, 3}, {3, 1}, {1, 2}, {2, 0}}, 4},
+	{3, [][]int{{1, 2}, {1, 2}, {2, 2}, {0, 2}, {2, 1}, {1, 1}, {1, 2}}, 4},
+}
+
+func TestMaxTransfers(t *testing.T) {
+	assert := assert.New(t)
+
+	for _, tc := range TestCases {
+		want := tc.Expected
+		got := maximumRequests(tc.N, tc.Requests)
+		assert.Equal(want, got, fmt.Sprintf("%+v", tc))
+	}
+}
+
+func BenchmarkMaxTransfers(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range TestCases {
+			maximumRequests(tc.N, tc.Requests)
+		}
+	}
+}

readme.md

@@ -439,6 +439,7 @@ Each problem is in it's own directory, with test files. There are helper package
 | 1575 | [Count All Possible Routes](https://leetcode.com/problems/count-all-possible-routes) | [My Solution](./problems/problem1575) | ✅ |
 | 1578 | [Minimum Time to Make Rope Colorful](https://leetcode.com/problems/minimum-time-to-make-rope-colorful) | [My Solution](./problems/problem1578) | ✅ |
 | 1579 | [Remove Max Number of Edges to Keep Graph Fully Traversable](https://leetcode.com/problems/remove-max-number-of-edges-to-keep-graph-fully-traversable) | [My Solution](./problems/problem1579) | ✅ |
+| 1601 | [Maximum Number of Achievable Transfer Requests](https://leetcode.com/problems/maximum-number-of-achievable-transfer-requests) | [My Solution](./problems/problem1601) | ✅ |
 | 1603 | [Design Parking System](https://leetcode.com/problems/design-parking-system) | [My Solution](./problems/problem1603) | ✅ |
 | 1609 | [Even Odd Tree](https://leetcode.com/problems/even-odd-tree) | [My Solution](./problems/problem1609) | ✅ |
 | 1626 | [Best Team With No Conflicts](https://leetcode.com/problems/best-team-with-no-conflicts) | [My Solution](./problems/problem1626) | ✅ |