Week7_SunghunKim

snughnu/6주차_우선순위큐/11286.swift

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+// 백준_11286 절댓값 힙
+/*
+ 오답1. 절대값이 같은 값이 여러 개일 경우에는 작은 수를 먼저 출력해야함
+ */
+func solution(_ calculations: [Int]) {
+    var heap: [Int] = [0]           // heap[0]은 0으로 더미 값
+
+    func insert(_ value: Int) {
+        heap.append(value)
+
+        /* 오답 1
+        // bubble up
+        var index = heap.count - 1
+        while index > 1 && abs(heap[index]) < abs(heap[index/2]) {
+            heap.swapAt(index, index/2)
+            index /= 2
+        }
+         */
+
+        // bubble up
+        var index = heap.count - 1
+        while index > 1 {
+            let parent = index / 2
+            if abs(heap[index]) < abs(heap[parent]) ||
+               (abs(heap[index]) == abs(heap[parent]) &&
+                heap[index] < heap[parent]) {
+                heap.swapAt(index, parent)
+                index = parent
+            } else {
+                break
+            }
+        }
+    }
+
+    func removeMin() -> Int {
+        if heap.count == 1 {
+            return 0
+        } else if heap.count == 2 {
+            return heap.removeLast()
+        } else {
+            let minValue = heap[1]
+            heap[1] = heap.removeLast()
+
+            /*
+             오답1.
+
+            // bubble down
+            var index: Int = 1
+            while index*2 < heap.count {
+                var child = index * 2
+                if child + 1 < heap.count && abs(heap[child+1]) < abs(heap[child]) {
+                    child += 1
+                }
+
+                if abs(heap[index]) <= abs(heap[child]) { break }
+
+                heap.swapAt(index, child)
+                index = child
+            }
+
+             */
+            var index: Int = 1
+            while index * 2 < heap.count {
+                var child = index * 2
+                if child + 1 < heap.count &&
+                    (abs(heap[child + 1]) < abs(heap[child]) ||
+                     (abs(heap[child + 1]) == abs(heap[child]) &&
+                      heap[child + 1] < heap[child])) {
+                    child += 1
+                }
+
+                if abs(heap[index]) < abs(heap[child]) ||
+                   (abs(heap[index]) == abs(heap[child]) &&
+                    heap[index] <= heap[child]) {
+                    break
+                }
+
+                heap.swapAt(index, child)
+                index = child
+            }
+
+            return minValue
+        }
+    }
+
+    for calculation in calculations {
+        if calculation == 0 {
+            print(removeMin())
+        } else {
+            insert(calculation)
+        }
+    }
+}
+
+let n: Int = Int(readLine()!)!
+var calculations: [Int] = []
+for _ in (0..<n) {
+    calculations.append(Int(readLine()!)!)
+}
+solution(calculations)

snughnu/6주차_우선순위큐/2075.swift

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+// 백준 2075 N번째 큰 수
+
+/*
+최소힙 사용
+- 최대 n개까지 유지
+- 입력되는 수를 하나씩 힙에 삽입
+- 힙 크기가 n이 넘으면 루트(가장 작은 값) 제거
+- 마지막에 루트값이 n번째 큰 수가 됨
+ */
+
+/*
+ 오답1: solution1메서드: 배열을 사용해봤지만 역시 시간복잡도에서 문제가 됩니다.
+ 오답2: solution메서드: 구조체를 사용하면 조금 빨라져서 해봤는데 아직 문제가 됩니다.
+ */
+
+func solution1(_ arrays: [[Int]]) {
+    let n: Int = arrays.count
+
+    var heap: [Int] = [0]   // 0은 인덱스 처리를 위한 더미값,
+
+    func insert(_ value: Int) {
+        heap.append(value)
+
+        // bubble up
+        var index = heap.count - 1
+        while index > 1 && heap[index] < heap[index/2] {
+            heap.swapAt(index, index/2)
+            index /= 2
+        }
+    }
+
+    func removeMin() {
+        heap[1] = heap.removeLast()
+
+        // bubble down
+        var index = 1
+        while index*2 < heap.count {
+            var child = index*2
+            if child + 1 < heap.count &&
+                heap[child + 1] < heap[child] {
+                child += 1
+            }
+            if heap[index] <= heap[child] { break }
+
+            heap.swapAt(index, child)
+            index = child
+        }
+    }
+
+    for array in arrays {
+        for num in array {
+            if heap.count <= n {
+                insert(num)
+            } else if num > heap[1] {
+                removeMin()
+                insert(num)
+            }
+        }
+    }
+
+    print(heap[1])
+}
+
+// heap 구조체 정의
+struct MinHeap {
+    private var heap = [Int]()
+
+    init() {
+        heap.append(0)
+    }
+
+    var count: Int {
+        return heap.count - 1
+    }
+
+    var top: Int {
+        return heap[1]
+    }
+
+    mutating func insert(_ value: Int) {
+        heap.append(value)
+
+        // bubble up
+        var index = heap.count - 1
+        while index > 1 && heap[index] < heap[index/2] {
+            heap.swapAt(index, index/2)
+            index /= 2
+        }
+    }
+
+    mutating func removeMin() {
+        guard heap.count > 1 else { return }
+        heap.swapAt(1, heap.count - 1)
+        _ = heap.removeLast()
+
+        // bubble down
+        var index = 1
+        while index*2 < heap.count {
+            var child = index * 2
+            if child + 1 < heap.count &&
+                heap[child + 1] < heap[child] {
+                child += 1
+            }
+            if heap[index] <= heap[child] { break }
+
+            heap.swapAt(index, child)
+            index = child
+        }
+    }
+}
+
+func solution(_ arrays: [[Int]]) {
+    let n = arrays.count
+    var heap = MinHeap()
+
+    for array in arrays {
+        for num in array {
+            if heap.count < n {
+                heap.insert(num)
+            } else if num > heap.top {
+                heap.removeMin()
+                heap.insert(num)
+            }
+        }
+    }
+
+    print(heap.top)
+}
+
+let n: Int = Int(readLine()!)!
+var arrays: [[Int]] = []
+for _ in (0..<n) {
+    let line: [Int] = readLine()!.split(separator: " ").compactMap { Int($0) }
+    arrays.append(line)
+}
+
+solution(arrays)

snughnu/7주차_자유주제/Programmers_132265.swift

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+import Foundation
+
+/*
+오답: 시간초과
+func solution(_ topping: [Int]) -> Int {
+    var count: Int = 0
+
+    for i in (1..<topping.count) {
+        let leftSet = Set(Array(topping[..<i]))
+        let rightSet = Set(Array(topping[i...]))
+
+        if leftSet.count == rightSet.count { count += 1 }
+    }
+
+    return count
+}
+*/
+
+func solution(_ topping: [Int]) -> Int {
+    var count: Int = 0
+    var leftSet: Set<Int> = []
+    var rightDict: [Int: Int] = [:]
+
+    // 먼저 모든 토핑을 rightDict에 저장
+    for top in topping {
+        rightDict[top, default: 0] += 1
+    }
+
+    // 왼쪽에서 하나씩 늘려가면서 비교하기
+    for i in (0..<topping.count) {
+        let t = topping[i]
+        leftSet.insert(t)
+
+        rightDict[t]! -= 1
+        if rightDict[t]! == 0 {
+            rightDict.removeValue(forKey: t)
+        }
+
+        if leftSet.count == rightDict.count {
+            count += 1
+        }
+    }
+
+    return count
+}

snughnu/7주차_자유주제/Programmers_42586.swift

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+func solution(_ progresses: [Int], _ speeds: [Int]) -> [Int] {
+    // 남은 배포일 계산
+    var days: [Int] = []
+    for i in 0..<progresses.count {
+        let remainDay = ((100 - progresses[i]) + (speeds[i] - 1)) / speeds[i]
+        days.append(remainDay)
+    }
+
+    // 스택에 넣으면서 결과 만들기
+    var stack: [Int] = []
+    var result: [Int] = []
+    for day in days {
+        if stack.isEmpty {
+            stack.append(day)
+        } else if day <= stack.last! {              // day가 top과 같거나 작으면 같은 배포일
+            stack.append(stack.last!)
+        } else {                                    // day가 top보다 크면 날짜 기록하고, stack 초기화(pop)
+            result.append(stack.count)
+            stack = [day]
+        }
+    }
+
+    if !stack.isEmpty {
+        result.append(stack.count)
+    }
+
+    return result
+}
+
+// 스택을 사용하지 않는 버전
+func solution2(_ progresses: [Int], _ speeds: [Int]) -> [Int] {
+    var days: [Int] = []
+    for i in 0..<progresses.count {
+        let remainDay = ((100 - progresses[i]) + (speeds[i] - 1)) / speeds[i]
+        days.append(remainDay)
+    }
+
+    var result: [Int] = []
+    var current = days[0]
+    var count = 1
+
+    for i in 1..<days.count {
+        if days[i] <= current {
+            count += 1
+        } else {
+            result.append(count)
+            current = days[i]
+            count = 1
+        }
+    }
+
+    result.append(count)
+    return result
+}