Merge pull request #786 from 0xff-dev/1481

Add solution and test-cases for problem 1481

leetcode/1401-1500/1481.Least-Number-of-Unique-Integers-after-K-Removals/README.md

@@ -0,0 +1,27 @@
+# [1481.Least Number of Unique Integers after K Removals][title]
+
+## Description
+Given an array of integers `arr` and an integer `k`. Find the least number of unique integers after removing **exactly** `k` elements.
+
+**Example 1:**
+
+```
+Input: arr = [5,5,4], k = 1
+Output: 1
+Explanation: Remove the single 4, only 5 is left.
+```
+
+**Example 2:**
+
+```
+Input: arr = [4,3,1,1,3,3,2], k = 3
+Output: 2
+Explanation: Remove 4, 2 and either one of the two 1s or three 3s. 1 and 3 will be left.
+```
+
+## 结语
+
+如果你同我一样热爱数据结构、算法、LeetCode，可以关注我 GitHub 上的 LeetCode 题解：[awesome-golang-algorithm][me]
+
+[title]: https://leetcode.com/problems/least-number-of-unique-integers-after-k-removals
+[me]: https://github.com/kylesliu/awesome-golang-algorithm

leetcode/1401-1500/1481.Least-Number-of-Unique-Integers-after-K-Removals/Solution.go

@@ -1,5 +1,87 @@
 package Solution
 
-func Solution(x bool) bool {
+import (
+	"container/heap"
+)
+
+type eleCount struct {
+	n, c int
+}
+
+type eleCountList []eleCount
+
+func (e *eleCountList) Len() int {
+	return len(*e)
+}
+
+func (e *eleCountList) Less(i, j int) bool {
+	return (*e)[i].c < (*e)[j].c
+}
+func (e *eleCountList) Swap(i, j int) {
+	(*e)[i], (*e)[j] = (*e)[j], (*e)[i]
+}
+
+func (e *eleCountList) Push(x interface{}) {
+	*e = append(*e, x.(eleCount))
+}
+
+func (e *eleCountList) Pop() interface{} {
+	old := *e
+	l := len(old)
+	x := old[l-1]
+	*e = old[:l-1]
 	return x
 }
+func Solution(arr []int, k int) int {
+	nodeCache := make(map[int]int)
+	list := eleCountList{}
+	for _, n := range arr {
+		idx, ok := nodeCache[n]
+		if !ok {
+			list = append(list, eleCount{n: n, c: 1})
+			p := len(list) - 1
+			nodeCache[n] = p
+			continue
+		}
+		list[idx].c++
+	}
+	heap.Init(&list)
+	add := 0
+	for k > 0 && list.Len() > 0 {
+		top := heap.Pop(&list).(eleCount)
+		if top.c >= k {
+			if top.c != k {
+				add = 1
+			}
+			break
+		}
+		k -= top.c
+	}
+	return list.Len() + add
+}
+
+func Solution2(arr []int, k int) int {
+	count := make(map[int]int)
+	for _, n := range arr {
+		count[n]++
+	}
+	cc := [100001]int{}
+	for _, c := range count {
+		cc[c]++
+	}
+	remove := 0
+	for i := 1; i <= 100000; i++ {
+		if cc[i] == 0 {
+			continue
+		}
+
+		a := k / i
+		if a < cc[i] {
+			remove += a
+			break
+		}
+		k -= cc[i] * i
+		remove += cc[i]
+	}
+	return len(count) - remove
+}

leetcode/1401-1500/1481.Least-Number-of-Unique-Integers-after-K-Removals/Solution_test.go

@@ -10,30 +10,35 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		arr    []int
+		k      int
+		expect int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", []int{5, 5, 1}, 1, 1},
+		{"TestCase2", []int{4, 3, 1, 1, 3, 3, 2}, 3, 2},
 	}
 
 	//	开始测试
 	for i, c := range cases {
 		t.Run(c.name+" "+strconv.Itoa(i), func(t *testing.T) {
-			got := Solution(c.inputs)
+			got := Solution(c.arr, c.k)
 			if !reflect.DeepEqual(got, c.expect) {
-				t.Fatalf("expected: %v, but got: %v, with inputs: %v",
-					c.expect, got, c.inputs)
+				t.Fatalf("expected: %v, but got: %v, with inputs: %v %v",
+					c.expect, got, c.arr, c.k)
+			}
+			got = Solution2(c.arr, c.k)
+			if !reflect.DeepEqual(got, c.expect) {
+				t.Fatalf("expected: %v, but got: %v, with inputs: %v %v",
+					c.expect, got, c.arr, c.k)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }