从起始点以螺旋形式打印矩阵
原文： https://www.geeksforgeeks.org/print-matrix-spiral-form-starting-point/
给定大小为n * m的矩阵和点P(c, r)。 从点P开始以螺旋形式（顺时针）打印矩阵。
示例：
Input : mat[][] = {{1 2 3},
{4 5 6},
{7 8 9}}
Point P = (0, 2)
Output : 3 6 5 2 9 8 7 4 1
The starting point is top left which
is 3.
这个问题主要是以螺旋形式打印矩阵的扩展。
C++
// C++ program to print a matrix in spiral
// form.
#include <iostream>
using namespace std;
const int MAX = 100;
void printSpiral(int mat[][MAX], int r, int c)
{
int i, a = 0, b = 2;
int low_row = (0 > a) ? 0 : a;
int low_column = (0 > b) ? 0 : b - 1;
int high_row = ((a + 1) >= r) ? r - 1 : a + 1;
int high_column = ((b + 1) >= c) ? c - 1 : b + 1;
while ((low_row > 0 - r && low_column > 0 - c)) {
for (i = low_column + 1; i <= high_column &&
i < c && low_row >= 0; ++i)
cout << mat[low_row][i] << " ";
low_row -= 1;
for (i = low_row + 2; i <= high_row && i < r &&
high_column < c; ++i)
cout << mat[i][high_column] << " ";
high_column += 1;
for (i = high_column - 2; i >= low_column &&
i >= 0 && high_row < r; --i)
cout << mat[high_row][i] << " ";
high_row += 1;
for (i = high_row - 2; i > low_row && i >= 0
&& low_column >= 0; --i)
cout << mat[i][low_column] << " ";
low_column -= 1;
}
cout << endl;
}
// Driver code
int main()
{
int mat[][MAX] = { { 1, 2, 3 }, { 4, 5, 6 }, { 7, 8, 9 } };
int r = 3, c = 3;
printSpiral(mat, r, c);
}
Java
// Java program to print a
// matrix in spiral form
import java.io.*;
class GFG {
static void printSpiral(int [][]mat, int r, int c)
{
int i, a = 0, b = 2;
int low_row = (0 > a) ? 0 : a;
int low_column = (0 > b) ? 0 : b - 1;
int high_row = ((a + 1) >= r) ? r - 1 : a + 1;
int high_column = ((b + 1) >= c) ? c - 1 : b + 1;
while ((low_row > 0 - r && low_column > 0 - c))
{
for (i = low_column + 1; i <= high_column &&
i < c && low_row >= 0; ++i)
System.out.print (mat[low_row][i] + " ");
low_row -= 1;
for (i = low_row + 2; i <= high_row && i < r &&
high_column < c; ++i)
System.out.print(mat[i][high_column] + " ");
high_column += 1;
for (i = high_column - 2; i >= low_column &&
i >= 0 && high_row < r; --i)
System.out.print(mat[high_row][i] + " ");
high_row += 1;
for (i = high_row - 2; i > low_row && i >= 0
&& low_column >= 0; --i)
System.out.print(mat[i][low_column] +" ");
low_column -= 1;
}
System.out.println();
}
// Driver code
static public void main (String[] args)
{
int [][]mat = {{1, 2, 3},
{4, 5, 6},
{7, 8, 9}};
int r = 3, c = 3;
// Function calling
printSpiral(mat, r, c);
}
}
// This code is contributed by vt_m.
Python 3
# Python3 program to print a matrix
# in spiral form.
MAX = 100
def printSpiral(mat, r, c):
a = 0
b = 2
low_row = 0 if (0 > a) else a
low_column = 0 if (0 > b) else b - 1
high_row = r-1 if ((a + 1) >= r) else a + 1
high_column = c-1 if ((b + 1) >= c) else b + 1
while ((low_row > 0 - r and low_column > 0 - c)):
i = low_column + 1
while (i <= high_column and
i < c and low_row >= 0):
print( mat[low_row][i], end = " ")
i += 1
low_row -= 1
i = low_row + 2
while (i <= high_row and
i < r and high_column < c):
print(mat[i][high_column], end = " ")
i += 1
high_column += 1
i = high_column - 2
while (i >= low_column and
i >= 0 and high_row < r):
print(mat[high_row][i], end = " ")
i -= 1
high_row += 1
i = high_row - 2
while (i > low_row and
i >= 0 and low_column >= 0):
print(mat[i][low_column], end = " ")
i -= 1
low_column -= 1
print()
# Driver code
if __name__ == "__main__":
mat = [[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]]
r = 3
c = 3
printSpiral(mat, r, c)
# This code is contributed by ita_c
C#
// C# program to print a
// matrix in spiral form
using System;
class GFG {
static void printSpiral(int [,]mat, int r, int c)
{
int i, a = 0, b = 2;
int low_row = (0 > a) ? 0 : a;
int low_column = (0 > b) ? 0 : b - 1;
int high_row = ((a + 1) >= r) ? r - 1 : a + 1;
int high_column = ((b + 1) >= c) ? c - 1 : b + 1;
while ((low_row > 0 - r && low_column > 0 - c))
{
for (i = low_column + 1; i <= high_column &&
i < c && low_row >= 0; ++i)
Console.Write (mat[low_row,i] + " ");
low_row -= 1;
for (i = low_row + 2; i <= high_row && i < r &&
high_column < c; ++i)
Console.Write(mat[i,high_column] + " ");
high_column += 1;
for (i = high_column - 2; i >= low_column &&
i >= 0 && high_row < r; --i)
Console.Write(mat[high_row,i] + " ");
high_row += 1;
for (i = high_row - 2; i > low_row && i >= 0
&& low_column >= 0; --i)
Console.Write(mat[i,low_column] +" ");
low_column -= 1;
}
Console.WriteLine();
}
// Driver code
static public void Main ()
{
int [,]mat = {{1, 2, 3},
{4, 5, 6},
{7, 8, 9}};
int r = 3, c = 3;
// Function calling
printSpiral(mat, r, c);
}
}
// This code is contributed by vt_m.
PHP
<?php
// PHP program to print a
// matrix in spiral form.
$MAX = 100;
function printSpiral($mat,
$r, $c)
{
global $MAX;
$i; $a = 0; $b = 2;
$low_row = (0 > $a) ?
0 : $a;
$low_column = (0 > $b) ?
0 : $b - 1;
$high_row = (($a + 1) >= $r) ?
$r - 1 : $a + 1;
$high_column = (($b + 1) >= $c) ?
$c - 1 : $b + 1;
while (($low_row > 0 - $r &&
$low_column > 0 - $c))
{
for ($i = $low_column + 1;
$i <= $high_column &&
$i < $c && $low_row >= 0; ++$i)
echo $mat[$low_row][$i], " ";
$low_row -= 1;
for ($i = $low_row + 2;
$i <= $high_row && $i < $r &&
$high_column < $c; ++$i)
echo $mat[$i][$high_column] , " ";
$high_column += 1;
for ($i = $high_column - 2;
$i >= $low_column &&
$i >= 0 && $high_row < $r; --$i)
echo $mat[$high_row][$i] , " ";
$high_row += 1;
for ($i = $high_row - 2;
$i > $low_row && $i >= 0 &&
$low_column >= 0; --$i)
echo $mat[$i][$low_column] , " ";
$low_column -= 1;
}
echo "\n";
}
// Driver code
$mat = array(array(1, 2, 3),
array(4, 5, 6),
array(7, 8, 9));
$r = 3; $c = 3;
printSpiral($mat, $r, $c);
// This code is contributed by aj_36
?>
输出：
3 6 5 2 9 8 7 4 1
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