feat: Number of Islands #258

Author: donghyeon95

number-of-islands/donghyeon95.java

@@ -0,0 +1,34 @@
+class Solution {
+
+	int[][] moves = {{1,0}, {-1,0}, {0,1}, {0,-1}};
+	boolean[][] visited;
+	public int numIslands(char[][] grid) {
+		// 섬의 갯수 => 0혹은 경계선으로 둘러싸인 것의 갯수
+		// dfs로 탐색
+		int result = 0;
+		visited = new boolean[grid.length][grid[0].length];
+
+		for (int i=0; i<grid.length; i++) {
+			for (int j=0; j<grid[0].length; j++) {
+				if (grid[i][j] == '1' && !visited[i][j]) {
+					dfs(i, j, grid);
+					result++;
+				}
+			}
+		}
+
+		return result;
+	}
+
+	public void dfs(int y, int x, char[][] grid) {
+		visited[y][x] = true;
+
+		for (int[] move: moves) {
+			int newX = x + move[0];
+			int newY = y + move[1];
+
+			if (newX<0 || newX >= grid[0].length || newY<0 || newY >= grid.length || visited[newY][newX] || grid[newY][newX]=='0') continue;
+			dfs(newY, newX, grid);
+		}
+	}
+}