13주차 문제풀이 (김혜경)

baekjoon/11967_불켜기/src/Hyekyoung.java

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+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Queue;
+import java.util.StringTokenizer;
+
+public class Hyekyoung {
+
+	static int N, M, cnt = 1;
+	static boolean[][] map, visited;
+	static List<Point>[] switchMap;
+	static List<Point> room = new ArrayList<>();
+	static int[] dr = { -1, 1, 0, 0 }, dc = { 0, 0, -1, 1 };
+	static Queue<Point> queue = new ArrayDeque<>();
+
+	public static void main(String[] args) throws IOException {
+
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		StringTokenizer st = new StringTokenizer(br.readLine());
+		N = Integer.parseInt(st.nextToken());
+		M = Integer.parseInt(st.nextToken());
+		switchMap = new ArrayList[N * N + 1];
+		map = new boolean[N + 1][N + 1];
+		visited = new boolean[N + 1][N + 1];
+		int x, y, a, b;
+
+		for (int i = 1; i <= N * N; i++) switchMap[i] = new ArrayList<>();
+
+		for (int i = 0; i < M; i++) {
+			st = new StringTokenizer(br.readLine());
+			x = Integer.parseInt(st.nextToken());
+			y = Integer.parseInt(st.nextToken());
+			a = Integer.parseInt(st.nextToken());
+			b = Integer.parseInt(st.nextToken());
+
+			switchMap[(x - 1) * N + y].add(new Point(a, b));
+		}
+		lightOn();
+		System.out.println(cnt);
+	}
+
+	static void lightOn() {
+		map[1][1] = true;
+		Point curPoint;
+		Point p;
+		int nr, nc, r, c, pr, pc;
+		queue.offer(new Point(1, 1));
+		visited[1][1] = true;
+
+		while (!queue.isEmpty()) {
+			curPoint = queue.poll();
+			r = curPoint.r;
+			c = curPoint.c;
+
+			for (Point point : switchMap[(r - 1) * N + c]) {
+				pr = point.r;
+				pc = point.c;
+				if (!visited[pr][pc]) {
+					map[pr][pc] = true;
+					cnt++;
+					room.add(new Point(pr, pc));
+				}
+				// 현재 위치에서 불을 켤 수 있는곳은 켜고 리스트에 추가
+			}
+
+			for (int i=0; i<room.size(); i++) {
+				p = room.get(i);
+				pr = p.r;
+				pc = p.c;
+				if (isConnected(r, c, pr, pc) && !visited[pr][pc]) {
+					visited[pr][pc] = true;
+					queue.offer(new Point(pr, pc));
+					room.remove(i);
+					i--;
+				}
+				// 리스트에 있는 목록 중 갈 수 있는 곳은 큐에 넣고 리스트에서 빼기
+			}
+
+		}
+	}
+
+	static boolean isConnected(int sr, int sc, int er, int ec) {
+		// 현재 위치에서 갈 수 있는 곳인지 판단
+		queue.offer(new Point(sr, sc));
+		int r, c, nr, nc;
+		Point curPoint;
+		boolean[][] check = new boolean[N + 1][N + 1];
+		check[sr][sc] = true;
+
+		while (!queue.isEmpty()) {
+			curPoint = queue.poll();
+			r = curPoint.r;
+			c = curPoint.c;
+
+			if (r == er && c == ec) {
+				return true;
+			}
+
+			for (int i = 0; i < 4; i++) {
+				nr = r + dr[i];
+				nc = c + dc[i];
+
+				if (nr < 1 || nc < 1 || nr > N || nc > N) continue;
+				if (!map[nr][nc] || check[nr][nc]) continue;
+
+				check[nr][nc] = true;
+				queue.offer(new Point(nr, nc));
+			}
+		}
+		return false;
+	}
+
+	static class Point {
+		int r, c;
+
+		public Point(int r, int c) {
+			super();
+			this.r = r;
+			this.c = c;
+		}
+	}
+}

baekjoon/14908_구두수선공/src/Hyekyoung.java

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+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.Arrays;
+import java.util.StringTokenizer;
+
+public class Hyekyoung {
+
+	public static void main(String[] args) throws IOException {
+
+		StringBuilder sb = new StringBuilder();
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		int N = Integer.parseInt(br.readLine());
+		Work[] works = new Work[N];
+		double a, b;
+		StringTokenizer st;
+		for(int i=0; i<N; i++) {
+			st = new StringTokenizer(br.readLine());
+			a = Double.parseDouble(st.nextToken());
+			b = Double.parseDouble(st.nextToken());
+			works[i] = new Work(i+1, a/b);
+		}
+		Arrays.sort(works);
+		for (Work work : works) {
+			sb.append(work.index+"\n");
+		}
+		System.out.println(sb.toString());
+	}
+
+	static class Work implements Comparable<Work>{
+		int index;
+		double per;
+
+		public Work(int index, double compensation) {
+			super();
+			this.index = index;
+			this.per = compensation;
+		}
+
+		@Override
+		public int compareTo(Work o) {
+			return Double.compare(this.per, o.per);
+		}
+	}
+}

baekjoon/14927_전구끄기/src/Hyekyoung.java

@@ -0,0 +1,81 @@
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.StringTokenizer;
+
+public class Hyekyoung {
+
+	static int N, minCnt = 325, push;
+	static int light[], selected, copy[], l, pos;
+
+	public static void main(String[] args) throws IOException {
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		N = Integer.parseInt(br.readLine());
+		light = new int[N];
+		int input;
+		StringTokenizer st;
+		for (int i = 0; i < N; i++) {
+			st = new StringTokenizer(br.readLine());
+			for (int j = 0; j < N; j++) {
+				input = Integer.parseInt(st.nextToken());
+				if (input == 1) light[i] |= (1 << j);
+				// 불 켜진 곳 표시
+			}
+		}
+		selectTop(0, 0);
+		System.out.println(minCnt < 325 ? minCnt : -1);
+	}
+
+	// 가장 윗줄 모든 경우 선택
+	static void selectTop(int cnt, int selected) {
+		if (cnt == N) {
+			lightOff(selected);
+			return;
+		}
+		selectTop(cnt + 1, selected);
+		selected |= 1 << cnt;
+		selectTop(cnt + 1, selected);
+	}
+
+	static void lightOff(int selected) {
+		copy = light.clone();
+		push = 0;
+		boolean flag = true;
+		l = selected & (-selected);
+		// 현재 열 바로 윗줄에서 가장 오른쪽에 위치한 1 비트 위치 찾기
+		// 내 윗 전구가 1이면 꺼야함(윗 줄을 끌 수 있는 것은 아랫줄 뿐이니까)
+		while (l > 0) {
+			pos = log2(l);
+			changeLight(0, pos);
+			selected &= ~(1 << pos);
+			l = selected & (-selected);
+		}
+		for (int i = 1; i < N; i++) {
+			l = copy[i - 1] & (-copy[i - 1]);
+			while (l > 0) {
+				changeLight(i, log2(l));
+				l = copy[i - 1] & (-copy[i - 1]);
+			}
+		}
+		for (int i = 0; i < N; i++) {
+			if (copy[i] > 0) {
+				flag = false;
+				break;
+			}
+		}
+		if (flag) minCnt = Math.min(minCnt, push);
+	}
+
+	static void changeLight(int r, int c) {
+		push++;
+		copy[r] ^= 1 << c;
+		if (r > 0) copy[r - 1] ^= 1 << c;
+		if (r < N - 1) copy[r + 1] ^= 1 << c;
+		if (c > 0) copy[r] ^= 1 << c - 1;
+		if (c < N - 1) copy[r] ^= 1 << c + 1;
+	}
+
+	static int log2(int x) {
+		return (int) (Math.log(x) / Math.log(2));
+	}
+}

programmers/섬연결하기/src/Hyekyoung.java

@@ -0,0 +1,85 @@
+import java.util.Arrays;
+
+//간많프 간선이 적으면 크루스칼!
+public class Hyekyoung {
+	public static void main(String[] args) {
+
+		int n = 4;
+		int[][] costs = new int[][] { { 0, 1, 1 }, { 0, 2, 2 }, { 1, 2, 5 }, { 1, 3, 1 }, { 2, 3, 8 } };
+		Solution s = new Solution();
+		if (s.solution(n, costs) == 4) {
+			System.out.println("정답");
+		} else {
+			System.out.println("땡");
+		}
+
+	}
+}
+
+class Edge implements Comparable<Edge> {
+	int from, to, weight;
+
+	public Edge(int from, int to, int weight) {
+		super();
+		this.from = from;
+		this.to = to;
+		this.weight = weight;
+	}
+
+	@Override
+	public int compareTo(Edge o) {
+		return Integer.compare(this.weight, o.weight);
+	}
+}
+
+class Solution {
+	int V, E;
+	Edge[] edgeList;
+	int[] parents;
+
+	void makeSet() {
+		parents = new int[V];
+		for (int i = 0; i < V; i++) {
+			parents[i] = i;
+		}
+	}
+
+	int findSet(int a) {
+		if (a == parents[a]) return a;
+		return parents[a] = findSet(parents[a]);
+	}
+
+	boolean union(int a, int b) {
+		int aRoot = findSet(a);
+		int bRoot = findSet(b);
+
+		if (aRoot == bRoot) return false;
+
+		parents[bRoot] = aRoot;
+		return true;
+	}
+
+	public int solution(int n, int[][] costs) {
+		V = n;
+		E = costs.length;
+
+		edgeList = new Edge[E];
+
+		for (int i = 0; i < E; i++) {
+			edgeList[i] = new Edge(costs[i][0], costs[i][1], costs[i][2]);
+		}
+
+		Arrays.sort(edgeList);
+		makeSet();
+		int result = 0, count = 0;
+
+		for (Edge edge : edgeList) {
+			if (union(edge.from, edge.to)) {
+				result += edge.weight;
+				if (++count == V - 1) break;
+			}
+		}
+
+		return result;
+	}
+}