Paste_Image.png

My code:

import java.util.ArrayList;
import java.util.List;

public class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        ArrayList<Integer> result = new ArrayList<Integer>();
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0)
            return result;
        int row = matrix.length;
        int col = matrix[0].length;
        for (int i = 0; i < Math.min(row, col); i++) {
            int temp = spiralOrder(i, row - 2 * i, col - 2 * i, matrix, result);
            if (temp == -1)
                break;
        }
        return result;
    }
    
    private int spiralOrder(int begin, int rowCount, int colCount, int[][] matrix, ArrayList<Integer> result) {
        if (rowCount <= 0 || colCount <= 0)
            return -1;
        else if (colCount == 1) {
            for (int i = 0; i < rowCount; i++)
                result.add(matrix[i + begin][begin]);
            return -1;
        }
        else if (rowCount == 1) {
            for (int i = 0; i < colCount; i++)
                result.add(matrix[begin][i + begin]);
            return -1;
        }
        
        int row = matrix.length - 1 - (matrix.length - rowCount) / 2;
        int col = matrix[0].length - 1 - (matrix[0].length - colCount) / 2;
        
        for (int i = begin; i <= col; i++)
            result.add(matrix[begin][i]);           
        for (int i = begin + 1; i <= row; i++)
            result.add(matrix[i][col]);
        for (int i = col - 1; i >= begin; i--)
            result.add(matrix[row][i]);
        for (int i = row - 1; i > begin; i--)
            result.add(matrix[i][begin]);
        return 1;
    }
    
    public static void main(String[] args) {
        Solution test = new Solution();
        int[][] a = new int[3][3];
        a[0][0] = 1;
        a[0][1] = 2;
        a[0][2] = 3;
        a[1][0] = 4;
        a[1][1] = 5;
        a[1][2] = 6;
        a[2][0] = 7;
        a[2][1] = 8;
        a[2][2] = 9;
        System.out.println(test.spiralOrder(a));
    }
}

My test result:

Paste_Image.png

这次题目我的代码运行素的比较慢，估计原因就是因为我设计了子函数，而本质上这道题目是不需要子函数的。所以速度会快很多。但这道题本身没有什么亮点，就这样吧。

Anyway, Good luck, Richardo!

My code:

public class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        ArrayList<Integer> ret = new ArrayList<Integer>();
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0)
            return ret;
        int width = matrix[0].length;
        int height = matrix.length;
        int i = 0;
        int j = 0;
        /** traversal every existed circle */
        while (j + width - 1 < matrix[0].length && i + height - 1 < matrix.length) {
            traversal(j, i, width, height, matrix, ret);
            i++;
            j++;
            width = width - 2;
            height = height - 2;
            if (width <= 0 || height <= 0) // if width or height <= 0, quit
                break;
        }
        return ret;
    }
    /** traverse this circle */
    private void traversal(int beginCol, int beginRow, int width, int height, int[][] matrix, ArrayList<Integer> ret) {
        for (int i = beginCol; i < beginCol + width; i++)
            ret.add(matrix[beginRow][i]);
        if (height == 1)
            return;
        for (int i = beginRow + 1; i < beginRow + height; i++)
            ret.add(matrix[i][beginCol + width - 1]);
        if (width == 1)
            return;
        for (int i = beginCol + width - 2; i >= beginCol; i--)
            ret.add(matrix[beginRow + height - 1][i]);
        for (int i = beginRow + height - 2; i >= beginRow + 1; i--)
            ret.add(matrix[i][beginCol]);
    }
}

这道题目不难，但是很烦。妈的。。。
感觉第二次写的要简洁一些。

Anyway, Good luck, Richardo!

My code:

public class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> ret = new ArrayList<Integer>();
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
            return ret;
        }
        int rowBegin = 0;
        int rowEnd = matrix.length - 1;
        int colBegin = 0;
        int colEnd = matrix[0].length - 1;
        
        while (rowBegin <= rowEnd && colBegin <= colEnd) {
            for (int i = colBegin; i <= colEnd; i++) {
                ret.add(matrix[rowBegin][i]);
            }
            rowBegin++;
            
            for (int i = rowBegin; i <= rowEnd; i++) {
                ret.add(matrix[i][colEnd]);
            }
            colEnd--;
            
            if (rowBegin <= rowEnd) {
                for (int i = colEnd; i >= colBegin; i--) {
                    ret.add(matrix[rowEnd][i]);
                }
                rowEnd--;
            }
            
            if (colBegin <= colEnd) {
                for (int i = rowEnd; i >= rowBegin; i--) {
                    ret.add(matrix[i][colBegin]);
                }
                colBegin++;
            }
        }
        return ret;
    }
}

第一次知道，恶心的题目得看论坛，都有最优解！
以后每道题目，都看下论坛投票最高的解法。
这个解法就很自然，也容易记住，避免了许多corner case
同时，记住这里，需要判断
if (rowBegin <= rowEnd)
if (colBegin <= colEnd)

参考：
https://discuss.leetcode.com/topic/3713/super-simple-and-easy-to-understand-solution

Anyway, Good luck, Richardo! --- 08/11/2016