[프로그래머스 LV02] 석유 시추 (pccp 기출 2번) - BFS, 완탐

Author: HiiWee

hoseok/week35/ProgrammersPccp2.java

@@ -0,0 +1,79 @@
+import java.util.*;
+
+class Solution {
+
+    static class Node {
+        int r, c;
+
+        Node(int r, int c) {
+            this.r = r;
+            this.c = c;
+        }
+    }
+
+    private final int[] rows = {-1, 0, 1, 0};
+    private final int[] cols = {0, 1, 0, -1};
+
+    private int n, m;
+    private int[][] map;
+    private int[][] visited;
+    private Map<Integer, Integer> areaSizes = new HashMap<>();
+
+    public int solution(int[][] land) {
+        map = land;
+        n = map.length;
+        m = map[0].length;
+        visited = new int[n][m];
+
+        int areaNumber = 1;
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                if (visited[i][j] == 0 && map[i][j] > 0) {
+                    int size = bfs(areaNumber, new Node(i, j));
+                    areaSizes.put(areaNumber++, size);
+                }
+            }
+        }
+
+        int maxSum = 0;
+        for (int i = 0; i < m; i++) {
+            boolean[] areaVisited = new boolean[areaNumber];
+            int currentSum = 0;
+            for (int j = 0; j < n; j++) {
+                if (map[j][i] == 1 && !areaVisited[visited[j][i]]) {
+                    areaVisited[visited[j][i]] = true;
+                    currentSum += areaSizes.get(visited[j][i]);
+                }
+            }
+            maxSum = Math.max(currentSum, maxSum);
+        }
+
+        return maxSum;
+    }
+
+    public int bfs(int areaNumber, Node startNode) {
+        Queue<Node> que = new LinkedList<>();
+        visited[startNode.r][startNode.c] = areaNumber;
+        que.offer(startNode);
+
+        int size = 1;
+        while (!que.isEmpty()) {
+            Node curNode = que.poll();
+
+            for (int i = 0; i < 4; i++) {
+                int nextR = curNode.r + rows[i];
+                int nextC = curNode.c + cols[i];
+
+                if (nextR < 0 || nextR >= n || nextC < 0 || nextC >= m) {
+                    continue;
+                }
+                if (visited[nextR][nextC] == 0 && map[nextR][nextC] == 1) {
+                    size++;
+                    visited[nextR][nextC] = areaNumber;
+                    que.offer(new Node(nextR, nextC));
+                }
+            }
+        }
+        return size;
+    }
+}