How does the following function do the recursive backtracking? What is the base case for this function?

Let's say that the function is try to generate a maze, start from a point and move 2 cells everytime.

If it starts from (3,5), -> (5,5) -> (5,7) -> (7,7), then it hits dead end. How does it backtrack to last path?

public void recursion(int r, int c) { // 4 random directions int[] randDirs = generateRandomDirections(); // Examine each direction for (int i = 0; i < randDirs.length; i++) { switch(randDirs[i]){ case 1: // Up //Whether 2 cells up is out or not if (r - 2 <= 0) continue; if (maze[r - 2][c] != 0) { maze[r-2][c] = 0; maze[r-1][c] = 0; recursion(r - 2, c); } break; case 2: // Right // Whether 2 cells to the right is out or not if (c + 2 >= width - 1) continue; if (maze[r][c + 2] != 0) { maze[r][c + 2] = 0; maze[r][c + 1] = 0; recursion(r, c + 2); } break; case 3: // Down // Whether 2 cells down is out or not if (r + 2 >= height - 1) continue; if (maze[r + 2][c] != 0) { maze[r+2][c] = 0; maze[r+1][c] = 0; recursion(r + 2, c); } break; case 4: // Left // Whether 2 cells to the left is out or not if (c - 2 <= 0) continue; if (maze[r][c - 2] != 0) { maze[r][c - 2] = 0; maze[r][c - 1] = 0; recursion(r, c - 2); } break; } } }