LeetCode 54 螺旋矩阵

func spiralOrder(matrix [][]int) []int {  
    // special  
    if 0 == len(matrix) {  
        return []int{}  
    }  
  
    // standard  
    var elements []int  
  
    leftBoundary, rightBundary := 0, len(matrix[0])-1  
    topBoundary, bottomBoundary := 0, len(matrix)-1  
  
    for leftBoundary < rightBundary &&  
        topBoundary < bottomBoundary {  
        // top  
        for j := leftBoundary; j < rightBundary; j++ {  
            elements = append(elements, matrix[topBoundary][j])  
        }  
  
        // right  
        for i := topBoundary; i < bottomBoundary; i++ {  
            elements = append(elements, matrix[i][rightBundary])  
        }  
  
        // bottom  
        for j := rightBundary; j > leftBoundary; j-- {  
            elements = append(elements, matrix[bottomBoundary][j])  
        }  
  
        // left  
        for i := bottomBoundary; i > topBoundary; i-- {  
            elements = append(elements, matrix[i][leftBoundary])  
        }  
  
        leftBoundary++  
        rightBundary--  
        topBoundary++  
        bottomBoundary--  
    }  
  
    if leftBoundary == rightBundary &&  
        topBoundary <= bottomBoundary {  
        for i := topBoundary; i <= bottomBoundary; i++ {  
            elements = append(elements, matrix[i][leftBoundary])  
        }  
        return elements  
    }  
  
    if topBoundary == bottomBoundary &&  
        leftBoundary <= rightBundary {  
        for j := leftBoundary; j <= rightBundary; j++ {  
            elements = append(elements, matrix[topBoundary][j])  
        }  
    }  
  
    return elements  
}