Leetcode54. Spiral matrix

Title transmission address : https://leetcode.cn/problems/spiral-matrix/

Operational efficiency :

The code is as follows :

 public static List<Integer> spiralOrder(int[][] matrix) {
    
        HashSet<String> set = new HashSet<>();
        int count = matrix.length * matrix[0].length;
        int direction = 0;// The direction we are going  0: From left to right  1: From the top down  2: From right to left  3: From bottom to top 
        List<Integer> list = new ArrayList<>();
        int rowIndex = 0;
        int colIndex = 0;
        while (list.size() < count) {
    
            int num = matrix[rowIndex][colIndex];
            list.add(num);
            String coordinate = rowIndex + ":" + colIndex;// coordinate 
            set.add(coordinate);
            //  Verify whether the next coordinate in the same direction of the current coordinate is out of bounds 
            boolean validNextCoordinate = validNextCoordinate(direction, coordinate, set, matrix);
            // From left to right 
            if (direction == 0) {
    
                if (validNextCoordinate) {
      // If you don't cross the border , Then continue to move to the right 
                    colIndex++;
                } else {
       // If you cross the border , Change direction 
                    direction = 1;
                    rowIndex++;  // Change direction , Then the coordinates of the next position should be below the current coordinates 
                }
                continue;
            }
            // From the top down 
            if (direction == 1) {
    
                if (validNextCoordinate) {
      // If you don't cross the border , Then continue to move down 
                    rowIndex++;
                } else {
       // If you cross the border , Change direction   Then the next step is to go left 
                    direction = 2;
                    colIndex--;
                }
                continue;
            }

            // From right to left 
            if (direction == 2) {
    
                if (validNextCoordinate) {
      // If you don't cross the border , Then keep moving to the left 
                    colIndex--;
                } else {
       // If you cross the border , Change direction   Then the next step is to go up 
                    direction = 3;
                    rowIndex--;
                }
                continue;
            }
            // From bottom to top 
            if (direction == 3) {
    
                if (validNextCoordinate) {
      // If you don't cross the border , Then continue to move up 
                    rowIndex--;
                } else {
       // If you cross the border , Change direction   Then the next step is to go to the right 
                    direction = 0;
                    colIndex++;
                }
            }
        }
        return list;
    }

    /** *  Verify whether the next coordinate in the same direction of the current coordinate is out of bounds  * * @param direction * @param coordinate * @param set * @param matrix * @return */
    public static boolean validNextCoordinate(Integer direction, String coordinate, HashSet<String> set, int[][] matrix) {
    
        String[] split = coordinate.split(":"); // Current coordinate position 
        int row = Integer.parseInt(split[0]);  // Coordinate position of current line 
        int col = Integer.parseInt(split[1]);  // Current column coordinate position 
        if (direction == 0) {
      // If it is from left to right 
            col++;   // Row coordinates unchanged , Shift the column coordinates to the right 
        }
        if (direction == 1) {
      // If it's from top to bottom 
            row++;   // The column coordinates do not change , Move the row coordinates down 
        }
        if (direction == 2) {
      // If it's from right to left 
            col--;   // Row coordinates unchanged , The column coordinates move left 
        }
        if (direction == 3) {
      // If it's from bottom to top 
            row--;   // The column coordinates do not change , Move the row coordinates up 
        }
        // First of all, make sure that the coordinates of the next position cannot exceed matrix The scope of 
        if (row >= matrix.length || row < 0 || col >= matrix[0].length || col < 0) {
    
            return false;
        }
        // Secondly, the coordinates of the next position cannot be set Inside 
        String nextCoordinate = row + ":" + col;
        return !set.contains(nextCoordinate);
    }