以反螺旋形式打印矩阵
原文： https://www.geeksforgeeks.org/print-matrix-antispiral-form/
给定 2D 数组，任务是以反螺旋形式打印矩阵：
示例：
输出：16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1。
Input : arr[][4] = {1, 2, 3, 4
5, 6, 7, 8
9, 10, 11, 12
13, 14, 15, 16};
Output : 10 11 7 6 5 9 13 14 15 16 12 8 4 3 2 1
Input :arr[][6] = {1, 2, 3, 4, 5, 6
7, 8, 9, 10, 11, 12
13, 14, 15, 16, 17, 18};
Output : 11 10 9 8 7 13 14 15 16 17 18 12 6 5 4 3 2 1
想法很简单，我们以螺旋形式 遍历矩阵，并将所有遍历的元素放入栈中。 最后从栈中逐一列出并打印它们。
C++
// C++ program to print matrix in anti-spiral form
#include <bits/stdc++.h>
using namespace std;
#define R 4
#define C 5
void antiSpiralTraversal(int m, int n, int a[R][C])
{
int i, k = 0, l = 0;
/* k - starting row index
m - ending row index
l - starting column index
n - ending column index
i - iterator */
stack<int> stk;
while (k <= m && l <= n)
{
/* Print the first row from the remaining rows */
for (i = l; i <= n; ++i)
stk.push(a[k][i]);
k++;
/* Print the last column from the remaining columns */
for (i = k; i <= m; ++i)
stk.push(a[i][n]);
n--;
/* Print the last row from the remaining rows */
if ( k <= m)
{
for (i = n; i >= l; --i)
stk.push(a[m][i]);
m--;
}
/* Print the first column from the remaining columns */
if (l <= n)
{
for (i = m; i >= k; --i)
stk.push(a[i][l]);
l++;
}
}
while (!stk.empty())
{
cout << stk.top() << " ";
stk.pop();
}
}
/* Driver program to test above functions */
int main()
{
int mat[R][C] =
{
{1, 2, 3, 4, 5},
{6, 7, 8, 9, 10},
{11, 12, 13, 14, 15},
{16, 17, 18, 19, 20}
};
antiSpiralTraversal(R-1, C-1, mat);
return 0;
}
Java
// Java Code for Print matrix in antispiral form
import java.util.*;
class GFG {
public static void antiSpiralTraversal(int m, int n,
int a[][])
{
int i, k = 0, l = 0;
/* k - starting row index
m - ending row index
l - starting column index
n - ending column index
i - iterator */
Stack<Integer> stk=new Stack<Integer>();
while (k <= m && l <= n)
{
/* Print the first row from the remaining
rows */
for (i = l; i <= n; ++i)
stk.push(a[k][i]);
k++;
/* Print the last column from the remaining
columns */
for (i = k; i <= m; ++i)
stk.push(a[i][n]);
n--;
/* Print the last row from the remaining
rows */
if ( k <= m)
{
for (i = n; i >= l; --i)
stk.push(a[m][i]);
m--;
}
/* Print the first column from the remaining
columns */
if (l <= n)
{
for (i = m; i >= k; --i)
stk.push(a[i][l]);
l++;
}
}
while (!stk.empty())
{
System.out.print(stk.peek() + " ");
stk.pop();
}
}
/* Driver program to test above function */
public static void main(String[] args)
{
int mat[][] =
{
{1, 2, 3, 4, 5},
{6, 7, 8, 9, 10},
{11, 12, 13, 14, 15},
{16, 17, 18, 19, 20}
};
antiSpiralTraversal(mat.length - 1, mat[0].length - 1,
mat);
}
}
// This code is contributed by Arnav Kr. Mandal.
Python 3
# Python 3 program to print
# matrix in anti-spiral form
R = 4
C = 5
def antiSpiralTraversal(m, n, a):
k = 0
l = 0
# k - starting row index
# m - ending row index
# l - starting column index
# n - ending column index
# i - iterator
stk = []
while (k <= m and l <= n):
# Print the first row
# from the remaining rows
for i in range(l, n + 1):
stk.append(a[k][i])
k += 1
# Print the last column
# from the remaining columns
for i in range(k, m + 1):
stk.append(a[i][n])
n -= 1
# Print the last row
# from the remaining rows
if ( k <= m):
for i in range(n, l - 1, -1):
stk.append(a[m][i])
m -= 1
# Print the first column
# from the remaining columns
if (l <= n):
for i in range(m, k - 1, -1):
stk.append(a[i][l])
l += 1
while len(stk) != 0:
print(str(stk[-1]), end = " ")
stk.pop()
# Driver Code
mat = [[1, 2, 3, 4, 5],
[6, 7, 8, 9, 10],
[11, 12, 13, 14, 15],
[16, 17, 18, 19, 20]];
antiSpiralTraversal(R - 1, C - 1, mat)
# This code is contributed
# by ChitraNayal
C
using System;
using System.Collections.Generic;
// C# Code for Print matrix in antispiral form
public class GFG
{
public static void antiSpiralTraversal(int m, int n, int[][] a)
{
int i, k = 0, l = 0;
/* k - starting row index
m - ending row index
l - starting column index
n - ending column index
i - iterator */
Stack<int> stk = new Stack<int>();
while (k <= m && l <= n)
{
/* Print the first row from the remaining
rows */
for (i = l; i <= n; ++i)
{
stk.Push(a[k][i]);
}
k++;
/* Print the last column from the remaining
columns */
for (i = k; i <= m; ++i)
{
stk.Push(a[i][n]);
}
n--;
/* Print the last row from the remaining
rows */
if (k <= m)
{
for (i = n; i >= l; --i)
{
stk.Push(a[m][i]);
}
m--;
}
/* Print the first column from the remaining
columns */
if (l <= n)
{
for (i = m; i >= k; --i)
{
stk.Push(a[i][l]);
}
l++;
}
}
while (stk.Count > 0)
{
Console.Write(stk.Peek() + " ");
stk.Pop();
}
}
/* Driver program to test above function */
public static void Main(string[] args)
{
int[][] mat = new int[][]
{
new int[] {1, 2, 3, 4, 5},
new int[] {6, 7, 8, 9, 10},
new int[] {11, 12, 13, 14, 15},
new int[] {16, 17, 18, 19, 20}
};
antiSpiralTraversal(mat.Length - 1, mat[0].Length - 1, mat);
}
}
// This code is contributed by Shrikant13
输出：
12 13 14 9 8 7 6 11 16 17 18 19 20 15 10 5 4 3 2 1
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