Method dfs

java/Graphs/CountIslands.java:20–34

(int r, int c, int[][] matrix)

    }

    private void dfs(int r, int c, int[][] matrix) {
        // Mark the current land cell as visited.
        matrix[r][c] = -1;
        // Define direction vectors for up, down, left, and right.
        int[][] dirs = new int[][]{{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
        // Recursively call DFS on each neighboring land cell to continue 
        // exploring this island.
        for (int[] d : dirs) {
            int nextR = r + d[0];
            int nextC = c + d[1];
            if (isWithinBounds(nextR, nextC, matrix) && matrix[nextR][nextC] == 1) {
                dfs(nextR, nextC, matrix);
            }
        }
    }

    private boolean isWithinBounds(int r, int c, int[][] matrix) {
        return 0 <= r && r < matrix.length && 0 <= c && c < matrix[0].length;