LeetCode 59 螺旋矩阵 II

func generateMatrix(n int) [][]int {  
    matrix := make([][]int, n)  
    for row := 0; row < len(matrix); row++ {  
        matrix[row] = make([]int, n)  
    }  
  
    v := 1  
    topBoundary, rightBoundary, bottomBoundary,  
        leftBoundary := 0, len(matrix[0]), len(matrix), 0  
    for topBoundary < bottomBoundary {  
        // top  
        for col := leftBoundary; col < rightBoundary; col++ {  
            matrix[topBoundary][col] = v  
            v++  
        }  
        topBoundary++  
  
        // right  
        for row := topBoundary; row < bottomBoundary; row++ {  
            matrix[row][rightBoundary-1] = v  
            v++  
        }  
        rightBoundary--  
  
        // bottom  
        for col := rightBoundary - 1; col >= leftBoundary; col-- {  
            matrix[bottomBoundary-1][col] = v  
            v++  
        }  
        bottomBoundary--  
  
        // left  
        for row := bottomBoundary - 1; row >= topBoundary; row-- {  
            matrix[row][leftBoundary] = v  
            v++  
        }  
        leftBoundary++  
    }  
  
    return matrix  
}