[김민진-2학기 1주차 알고리즘 스터디]

김민진/2학기/1주차/[Baekjoon-10159] 저울.java

@@ -0,0 +1,70 @@
+package semester2.week1;
+
+import java.io.*;
+import java.util.StringTokenizer;
+
+public class Q5Scale {
+
+	private static final BufferedReader  br = new BufferedReader(new InputStreamReader(System.in));
+	private static final BufferedWriter  bw = new BufferedWriter(new OutputStreamWriter(System.out));
+	private static final StringBuilder   sb = new StringBuilder();
+	private static       StringTokenizer st;
+
+	private static int N;
+	private static int M;
+
+	private static int[][] mat;
+
+	public static void main(String[] args) throws IOException {
+		init();
+		sol();
+	}
+
+	private static void init() throws IOException {
+		N = Integer.parseInt(br.readLine());
+		M = Integer.parseInt(br.readLine());
+
+		mat = new int[N + 1][N + 1];
+
+		for (int i = 0; i < M; i++) {
+			st = new StringTokenizer(br.readLine());
+
+			int a = Integer.parseInt(st.nextToken());
+			int b = Integer.parseInt(st.nextToken());
+
+			mat[a][b] = 1;  // big
+			mat[b][a] = -1; // small
+		}
+	}
+
+	private static void sol() throws IOException {
+		for (int k = 1; k < N + 1; k++) {
+			for (int i = 1; i < N + 1; i++) {
+				for (int j = 1; j < N + 1; j++) {
+					// big
+					if (mat[i][k] == 1 && mat[k][j] == 1) {
+						mat[i][j] = 1;
+
+						// small
+					} else if (mat[i][k] == -1 && mat[k][j] == -1) {
+						mat[i][j] = -1;
+					}
+				}
+			}
+		}
+
+		for (int i = 1; i < N + 1; i++) {
+			int cnt = 0;
+			for (int j = 1; j < N + 1; j++) {
+				if (i != j && mat[i][j] == 0) {
+					cnt++;
+				}
+			}
+			sb.append(cnt).append("\n");
+		}
+		bw.write(sb.toString());
+		bw.flush();
+		bw.close();
+	}
+
+}

김민진/2학기/1주차/[Baekjoon-1561] 놀이공원.java

@@ -0,0 +1,87 @@
+package semester2.week1;
+
+import java.io.*;
+import java.util.StringTokenizer;
+
+public class Q4AmusementPark {
+
+	private static final BufferedReader  br = new BufferedReader(new InputStreamReader(System.in));
+	private static final BufferedWriter  bw = new BufferedWriter(new OutputStreamWriter(System.out));
+	private static       StringTokenizer st;
+
+	private static int   N;
+	private static int   M;
+	private static int[] opTime;
+
+	public static void main(String[] args) throws IOException {
+		init();
+		sol();
+	}
+
+	private static void init() throws IOException {
+		st = new StringTokenizer(br.readLine());
+
+		N = Integer.parseInt(st.nextToken());
+		M = Integer.parseInt(st.nextToken());
+
+		opTime = new int[M];
+		st     = new StringTokenizer(br.readLine());
+		for (int i = 0; i < M; i++) {
+			opTime[i] = Integer.parseInt(st.nextToken());
+		}
+	}
+
+	private static void sol() throws IOException {
+		// 놀이기구 수가 많거나 같을 때
+		if (N <= M) {
+			bw.write(N + "");
+		} else {
+			long left       = 0;
+			long right      = N / M * 30L; // 최대 소요 시간
+			long targetTime = 0;
+
+			// N번째 아이가 탈 수 있는 시간 찾기
+			while (left <= right) {
+				long mid           = (left + right) / 2;
+				long totalChildren = M;
+
+				// mid 시간에 탈 수 있는 아이의 수
+				for (int i = 0; i < M; i++) {
+					totalChildren += mid / opTime[i];
+				}
+
+				// N명 이상의 아이가 탈 수 있음 → 범위 좁히기
+				if (totalChildren >= N) {
+					targetTime = mid;
+					right      = mid - 1;
+				} else {
+					left = mid + 1;
+				}
+			}
+			getAns(targetTime);
+		}
+		bw.flush();
+		bw.close();
+	}
+
+	private static void getAns(long time) throws IOException {
+		// N-1번째 아이가 타는 시간(time - 1)을 기반으로
+		long childrenBefore = M;
+		for (int i = 0; i < M; i++) {
+			childrenBefore += (time - 1) / opTime[i];
+		}
+
+		// N번째 아이가 어느 놀이기구에 타는지 찾기
+		// 이분탐색에서 N번째 아이가 탈 수 있는 최소 시간을 찾음
+		// 따라서 time일 때 최소 하나 이상의 비어있는 기구가 있음이 보장됨
+		for (int i = 0; i < M; i++) {
+			if (time % opTime[i] == 0) {
+				childrenBefore++;
+				if (childrenBefore == N) {
+					bw.write((i + 1) + "\n");
+					return;
+				}
+			}
+		}
+	}
+}

김민진/2학기/1주차/[Baekjoon-17390] 이건 꼭 풀어야해!.java

@@ -0,0 +1,62 @@
+package semester2.week1;
+
+import java.io.*;
+import java.util.Arrays;
+import java.util.StringTokenizer;
+
+public class Q3YouMustSolveThis {
+
+	private static final BufferedReader  br = new BufferedReader(new InputStreamReader(System.in));
+	private static final BufferedWriter  bw = new BufferedWriter(new OutputStreamWriter(System.out));
+	private static final StringBuilder   sb = new StringBuilder();
+	private static       StringTokenizer st;
+
+	private static int   A;
+	private static int   Q;
+	private static int[] nums;
+	private static int[] prefix;
+
+	public static void main(String[] args) throws IOException {
+		init();
+		sol();
+	}
+
+	private static void init() throws IOException {
+		st = new StringTokenizer(br.readLine());
+
+		A = Integer.parseInt(st.nextToken());
+		Q = Integer.parseInt(st.nextToken());
+
+		nums = new int[A + 1];
+		st   = new StringTokenizer(br.readLine());
+		for (int i = 1; i <= A; i++) {
+			nums[i] = Integer.parseInt(st.nextToken());
+		}
+		Arrays.sort(nums);
+
+		prefix = new int[A + 1];
+	}
+
+	private static void sol() throws IOException {
+		makePrefix();
+
+		while (Q-- > 0) {
+			st = new StringTokenizer(br.readLine());
+
+			int L = Integer.parseInt(st.nextToken());
+			int R = Integer.parseInt(st.nextToken());
+
+			sb.append(prefix[R] - prefix[L - 1]).append("\n");
+		}
+		bw.write(sb.toString());
+		bw.flush();
+		bw.close();
+	}
+
+	private static void makePrefix() {
+		for (int i = 1; i <= A; i++) {
+			prefix[i] = prefix[i - 1] + nums[i];
+		}
+	}
+
+}

김민진/2학기/1주차/[Baekjoon-2239] 스도쿠.java

@@ -0,0 +1,94 @@
+package semester2.week1;
+
+import java.io.*;
+
+public class Q1Sudoku {
+
+    private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    private static final BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    private static final StringBuilder sb = new StringBuilder();
+
+    private static char[][] input;
+
+    public static void main(String[] args) throws IOException {
+        init();
+        sol();
+    }
+
+    private static void init() throws IOException {
+        input = new char[9][9];
+
+        for (int i = 0; i < 9; i++) {
+            String str = br.readLine();
+
+            for (int j = 0; j < 9; j++) {
+                input[i][j] = str.charAt(j);
+            }
+        }
+    }
+
+    private static void sol() throws IOException {
+        if (dfs(0, 0)) {
+            for (int a = 0; a < 9; a++) {
+                for (int b = 0; b < 9; b++) {
+                    sb.append(input[a][b]);
+                }
+                sb.append("\n");
+            }
+            bw.write(sb.toString());
+            bw.flush();
+            bw.close();
+        }
+    }
+
+    private static boolean dfs(int i, int j) {
+        if (i >= 9) {
+            return true;
+        }
+
+        int nx = j == 8 ? i + 1 : i;
+        int ny = j == 8 ? 0 : j + 1;
+
+        if (input[i][j] != '0') return dfs(nx, ny);
+
+        for (int k = 1; k <= 9; k++) {
+            char val = (char) (k + '0');
+
+            input[i][j] = val;
+
+            if (isValid(i, j)) {
+                if (dfs(nx, ny)) {
+                    return true;
+                }
+            }
+            input[i][j] = '0';
+        }
+        return false;
+    }
+
+    private static boolean isValid(int x, int y) {
+        // vertical
+        for (int i = 0; i < 9; i++) {
+            if (i == x) continue;
+            if (input[i][y] == input[x][y]) return false;
+        }
+
+        // horizontal
+        for (int j = 0; j < 9; j++) {
+            if (j == y) continue;
+            if (input[x][j] == input[x][y]) return false;
+        }
+
+        // square
+        int a = x / 3 * 3;
+        int b = y / 3 * 3;
+        for (int i = a; i < a + 3; i++) {
+            for (int j = b; j < b + 3; j++) {
+                if (x == i && y == j) continue;
+                if (input[i][j] == input[x][y]) return false;
+            }
+        }
+        return true;
+    }
+
+}

김민진/2학기/1주차/[Baekjoon-9935] 문자열 폭발.java

@@ -0,0 +1,64 @@
+package semester2.week1;
+
+import java.io.*;
+import java.util.Stack;
+
+public class Q2StringEruption {
+
+    private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    private static final BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+
+    private static String haystack;
+    private static String needle;
+    private static int len;
+
+    private static Stack<Character> s;
+
+    public static void main(String[] args) throws IOException {
+        init();
+        sol();
+    }
+
+    private static void init() throws IOException {
+        haystack = br.readLine();
+        needle = br.readLine();
+        len = needle.length();
+
+        s = new Stack<>();
+    }
+
+    private static void sol() throws IOException {
+        for (int i = 0; i < haystack.length(); i++) {
+            s.push(haystack.charAt(i));
+
+            if (s.size() >= len && isNeedle()) {
+                for (int j = 0; j < len; j++) {
+                    s.pop();
+                }
+            }
+        }
+        printAns();
+    }
+
+    private static void printAns() throws IOException {
+        if (s.empty()) {
+            bw.write("FRULA");
+        } else {
+            for (char str : s) {
+                bw.write(str);
+            }
+        }
+        bw.flush();
+        bw.close();
+    }
+
+    private static boolean isNeedle() {
+        for (int i = 0; i < len; i++) {
+            if (!s.get(s.size() - len + i).equals(needle.charAt(i))) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+}