Python程序以蛇形模式打印矩阵

在本文中，我们将学习一个Python程序，以蛇形模式打印矩阵。

Assume we have taken the n x n matrix. We will now print the input matrix in a snake pattern using the below-mentioned methods.

Methods Used

The following are the various methods used to accomplish this task −

• 使用嵌套的for循环

• Reversing Alternate Rows Using Slicing

直觉 

我们将迭代遍历矩阵的所有行。对于每一行，我们将检查它是偶数还是奇数。如果行是偶数，则从左到右打印矩阵，否则从右到左打印矩阵。

Method 1: Using the nested for loop

算法（步骤）

以下是执行所需任务的算法/步骤。−

• Create a variable to store the number of rows of a matrix.

• Create another variable to store the number of columns of a matrix.

• 创建一个函数printSnakePattern()，通过接受输入矩阵作为参数以蛇形模式打印矩阵。

• Use the global keyword to make the rows and columns variables global.

• 使用for循环遍历矩阵的行。

• 使用if条件语句来检查当前行号是否为偶数。

• Use another nested for loop to traverse through all the columns of the current row if the condition is true.

• Print the matrix row from left to right if the current row is even.

• 否则，如果当前行是奇数，则从右到左打印矩阵行。

• Create a variable to store the input matrix and print the given matrix.

• 通过将输入矩阵作为参数调用上述定义的 printSnakePattern() 函数。

Example

以下程序使用嵌套的for循环以蛇形模式打印输入矩阵：

# initializing the number of rows of the matrix
rows = 4
# initializing the number of columns of the matrix
columns = 4
# creating a function for printing the matrix in
# snake pattern accepting the input matrix as an argument.
def printSnakePattern(inputMatrix):
   # making the rows and columns variables global
      global rows, columns
      # traversing through the rows of a matrix
      for m in range(rows):
         # checking whether the current row number is even
         if m % 2 == 0:
            # traversing through all the columns of the current row
               for n in range(columns):
                  # printing from left to right if the current row is even
                  print(inputMatrix[m][n], end=" ")

         # Else, printing from right to left if the current row is even
         else:
            # traversing from the end of the columns
               for n in range(columns - 1, -1, -1):
                  print(inputMatrix[m][n], end=" ")
# input matrix
inputMatrix = [[3, 4, 5, 6],
               [10, 40, 60, 80],
               [1, 9, 7, 8],
               [40, 20, 14, 15]]
print("The Given Matrix is :")
print(inputMatrix)
# calling the above-defined printSnakePattern function
# by passing the input matrix as an argument.
print("Snake Pattern of the given Matrix is:")
printSnakePattern(inputMatrix)

输出

On executing, the above program will generate the following output −

The Given Matrix is :
[[3, 4, 5, 6], [10, 40, 60, 80], [1, 9, 7, 8], [40, 20, 14, 15]]
Snake Pattern of the given Matrix is:
3 4 5 6 80 60 40 10 1 9 7 8 15 14 20 40 

方法2：使用切片反转交替行

slicing is a frequent practice and the one that programmers utilize the most to solve problems effectively. Consider a Python list. You must slice a list to access a range of list elements. The use of the colon(:), a simple slicing operator, is one method for accomplishing this.

Syntax

[start:stop:step]

参数

• start − 从哪里开始的索引

• end − ending index

• 步骤 − 在i之间要跳跃的次数，即步长

Example

以下程序使用切片以蛇形模式打印输入矩阵。

# input matrix
inputMatrix = [[3, 4, 5, 6],
               [10, 40, 60, 80],
               [1, 9, 7, 8],
               [40, 20, 14, 15]]
# initializing the number of rows of a matrix
rows = 4
# initializing the number of columns of a matrix
columns = 4
# creating a function for printing the matrix in
# snake pattern accepting the input matrix as an argument.
def printSnakePattern(inputMatrix):
   # making the rows and columns variables global
      global rows, columns
      # traversing through the rows of a matrix
      for m in range(rows):
         # checking whether the current row number is even
         if m % 2 != 0:
            # Reversing the row using reverse slicing
            inputMatrix[m] = inputMatrix[m][::-1]

      # traversing through the rows of a matrix
      for m in range(rows):
         # traversing through all the columns of the current row
         for n in range(columns):
            # printing the corresponding element
               print(inputMatrix[m][n], end=' ')
# input matrix
inputMatrix = [[3, 4, 5, 6],
               [10, 40, 60, 80],
               [1, 9, 7, 8],
               [40, 20, 14, 15]]
print("The Given Matrix is :")
print(inputMatrix)
# calling the above-defined printSnakePattern function
# by passing the input matrix as an argument.
print("Snake Pattern of the given Matrix is:")
printSnakePattern(inputMatrix)

输出

On execution, the above program will generate the following output −

The Given Matrix is :
[[3, 4, 5, 6], [10, 40, 60, 80], [1, 9, 7, 8], [40, 20, 14, 15]]
The Snake Pattern of the given Matrix is:
3 4 5 6 80 60 40 10 1 9 7 8 15 14 20 40 

Conclusion

In this article, we learned how to print the given matrix in snake form using two different methods. We learned how to use the global keyword to make variables global. We also learned how to reverse any iterable, including a list, tuple, string, etc. via reverse slicing.

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