Merge branch 'week12'

Author: spring0913

week12/BOJ_1038(감소하는 수).java

@@ -0,0 +1,30 @@
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    private static int N;
+    private static int count = 0;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        N = Integer.parseInt(br.readLine());
+        dfs(0, 11);
+        System.out.println("-1");
+    }
+
+    public static void dfs(long num, int index) {
+        if(index == 0) {
+            if(count == N) {
+                System.out.println(num);
+                System.exit(0);
+            }
+            count++;
+            return;
+        }
+        long k = (num == 0) ? 10 : num % 10;
+        for(long i=0; i<k; i++) {
+            dfs(num*10 + i, index-1);
+        }
+    }
+}

week12/BOJ_15270(친구 팰린드롬).java

@@ -0,0 +1,48 @@
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    private static int N, M;
+    private static boolean[][] friend;
+    private static int[][] relation;
+    private static boolean[] visited;
+    private static int answer = 0;
+
+    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());
+        friend = new boolean[N+1][N+1];
+        relation = new int[M][2];
+        visited = new boolean[N+1];
+        for(int i=0; i<M; i++) {
+            st = new StringTokenizer(br.readLine());
+            int u = Integer.parseInt(st.nextToken());
+            int v = Integer.parseInt(st.nextToken());
+            friend[u][v] = true;
+            friend[v][u] = true;
+            relation[i][0] = u;
+            relation[i][1] = v;
+        }
+        dfs(0, 0);
+        System.out.println((answer == N) ? answer : answer + 1);
+    }
+
+    public static void dfs(int start, int count) {
+        answer = Math.max(answer, count);
+
+        for(int i=start; i<M; i++) {
+            int friend1 = relation[i][0];
+            int friend2 = relation[i][1];
+            if(!visited[friend1] && !visited[friend2]) {
+                visited[friend1] = true;
+                visited[friend2] = true;
+                dfs(i, count+2);
+                visited[friend1] = false;
+                visited[friend2] = false;
+            }
+        }
+    }
+}

week12/BOJ_2661(좋은수열).java

@@ -0,0 +1,39 @@
+import java.io.*;
+
+public class Main {
+
+    private static int N;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        N = Integer.parseInt(br.readLine());
+        dfs("1");
+    }
+
+    public static void dfs(String strNum) {
+        if(strNum.length() == N) {
+            System.out.println(strNum);
+            System.exit(0);
+            return;
+        }
+
+        for(int j=1; j<=3; j++) {
+            String str = strNum + j;
+            if(check(str)) {
+                dfs(str);
+            }
+        }
+    }
+
+    public static boolean check(String strNum) {
+        int len = strNum.length();
+        for(int i=1; i<=len/2; i++) {
+            String str1 = strNum.substring(len-i, len);
+            String str2 = strNum.substring(len-i*2, len-i);
+            if(str1.equals(str2)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}

week12/Programmers_250136(석유 시추).java

@@ -0,0 +1,63 @@
+import java.util.*;
+
+class Solution {
+    private int[][] visited;
+    private int oilNum;
+    private Map<Integer, Integer> oilMap;
+    private int[][] land;
+
+    public int solution(int[][] _land) {
+        int answer = 0;
+        land = _land;
+        visited = new int[land.length][land[0].length];
+        oilNum = 1;
+        oilMap = new HashMap<>();
+        for(int i=0; i<land.length; i++) {
+            for(int j=0; j<land[0].length; j++) {
+                if(land[i][j] == 1 && visited[i][j] == 0) {
+                    bfs(i, j);
+                }
+            }
+        }
+        for(int i=0; i<land[0].length; i++) {
+            boolean[] check = new boolean[oilNum];
+            int count = 0;
+            for(int j=0; j<land.length; j++) {
+                int num = visited[j][i];
+                if(num > 0 && !check[num]) {
+                    check[num] = true;
+                    count += oilMap.get(num);
+                }
+            }
+            answer = Math.max(answer, count);
+        }
+        return answer;
+    }
+
+    public void bfs(int startH, int startW) {
+        int[] dh = {0, 1, 0, -1};
+        int[] dw = {-1, 0, 1, 0};
+        Queue<int[]> q = new LinkedList<>();
+        q.offer(new int[]{startH, startW});
+        visited[startH][startW] = oilNum;
+        int count = 1;
+        while(!q.isEmpty()) {
+            int h = q.peek()[0];
+            int w = q.peek()[1];
+            q.poll();
+            for(int i=0; i<4; i++) {
+                int nextH = h + dh[i];
+                int nextW = w + dw[i];
+                if(nextH >= 0 && nextH < land.length && nextW >= 0 && nextW < land[0].length) {
+                    if(land[nextH][nextW] == 1 && visited[nextH][nextW] == 0) {
+                        visited[nextH][nextW] = oilNum;
+                        q.offer(new int[]{nextH, nextW});
+                        count++;
+                    }
+                }
+            }
+        }
+        oilMap.put(oilNum, count);
+        oilNum++;
+    }
+}