Spiral Matrix

Problem: Spiral Matrix

The general idea is to set boundary for us and keep going until meet bound then we turn right and modify bounds.

Code in Python:

class Solution(object):
    def spiralOrder(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: List[int]
        """
        if not matrix: return []
        up, down, left, right = 0, len(matrix), -1, len(matrix[0])
        ans = []
        direction = 1
        while left < right and up < down:
            if direction == 1:
                for i in xrange(left+1, right):
                    ans.append(matrix[up][i])
                direction = 2
                right -= 1
                continue
            if direction == 2:
                for i in xrange(up+1, down):
                    ans.append(matrix[i][right])
                direction = 3
                down -= 1
                continue
            if direction == 3:
                for i in xrange(right-1, left, -1):
                    ans.append(matrix[down][i])
                direction = 4
                left += 1
                continue
            if direction == 4:
                for i in xrange(down-1, up, -1):
                    ans.append(matrix[i][left])
                direction = 1
                up += 1
                continue
        return ans

There's a cooler solution use a number to mark which round we are running.