number of islands

Author: se6816

number-of-islands/se6816.java

@@ -0,0 +1,52 @@
+/**
+    방문하지 않는 지점을 찾고, BFS로 인근 지점을 방문처리하며, 방문하지 않는 지점 개수를 카운틷하는 방식
+ */
+class Solution {
+    int M;
+    int N;
+    boolean[][] visited;
+    int[] moveX = {-1, 0, 0, 1};
+    int[] moveY = {0, -1, 1, 0};
+    public int numIslands(char[][] grid) {
+        int result = 0;
+        M = grid.length;
+        N = grid[0].length;
+        visited= new boolean[M][N];
+        for(int i = 0; i < M; i++) {
+            for(int j = 0; j < N; j++) {
+                if(!visited[i][j] && grid[i][j] == '1') {
+                    visited[i][j] = true;
+                    result++;
+                    paint(i, j, visited, grid);
+                }
+            }
+        }
+        return result;
+        
+    }
+    public void paint(int x, int y, boolean[][] visited, char[][] grid) {
+        for(int i = 0; i < 4; i++) {
+            int tempX = x + moveX[i];
+            int tempY = y + moveY[i];
+
+            if(isOutOfIndex(tempX, tempY)) {
+                continue;
+            }
+
+            if(visited[tempX][tempY]) {
+                continue;
+            }
+
+            if(grid[tempX][tempY] == '0') {
+                continue;
+            }
+
+            visited[tempX][tempY] = true;
+
+            paint(tempX,tempY, visited, grid);
+        }
+    }
+    public boolean isOutOfIndex(int x, int y) {
+        return x < 0 || x >= M || y < 0 || y >=N;
+    }
+}