Print Matrix in Spiral Form

Problem

Given an integer matrix, print it in spiral form

Sample Input

[1 2 3 4]
[4 5 6 7]
[8 9 10 11]

Sample Output

1 2 3 4 7 11 10 9 8 4 5 6

Approach

We can maintain four variables and four for loops to traverse four edges of the matrix. The edges keep on shrinking after every iteration around the matrix. The time complexity of the approach is O(MxN).

C++

#include <iostream>
#include <vector>
usingnamespacestd;
voidsolve(vector<vector<int>> matrix, int top, int bottom, int left, int right)
{
 if (matrix.size() == 0 || left > right) {
 return;
 }
 // print top row
 for (int i = left; i <= right; i++) {
 cout << matrix[top][i] << " ";
 }
 top++;
 if (top > bottom) {
 return;
 }
 // print right column
 for (int i = top; i <= bottom; i++) {
 cout << matrix[i][right] << " ";
 }
 right--;
 if (left > right) {
 return;
 }
 // print bottom row
 for (int i = right; i >= left; i--) {
 cout << matrix[bottom][i] << " ";
 }
 bottom--;
 if (top > bottom) {
 return;
 }
 // print left column
 for (int i = bottom; i >= top; i--) {
 cout << matrix[i][left] << " ";
 }
 left++;
 solve(matrix, top, bottom, left, right);
}
intmain()
{
 vector<vector<int>> matrix =
 {
 { 1, 2, 3, 4, 5},
 {16, 17, 18, 19, 6},
 {15, 24, 25, 20, 7}
 };
 int top = 0, bottom = matrix.size() - 1;
 int left = 0, right = matrix[0].size() - 1;
 solve(matrix, top, bottom, left, right);
 return0;
}

Output

1 2 3 4 5 6 7 20 25 24 15 16 17 18 19

C

#include<stdio.h>
voidsolve(int matrix[3][5], int top, int bottom, int left, int right)
{
 if (left > right) {
 return;
 }
 // print top row
 for (int i = left; i <= right; i++) {
 printf("%d ",matrix[top][i]);
 }
 top++;
 if (top > bottom) {
 return;
 }
 // print right column
 for (int i = top; i <= bottom; i++) {
 printf("%d ",matrix[i][right]);
 }
 right--;
 if (left > right) {
 return;
 }
 // print bottom row
 for (int i = right; i >= left; i--) {
 printf("%d ",matrix[bottom][i]);
 }
 bottom--;
 if (top > bottom) {
 return;
 }
 // print left column
 for (int i = bottom; i >= top; i--) {
 printf("%d ",matrix[i][left]);
 }
 left++;
 solve(matrix, top, bottom, left, right);
}
intmain()
{
 int matrix[3][5] =
 {
 { 1, 2, 3, 4, 5},
 {16, 17, 18, 19, 6},
 {15, 24, 25, 20, 7}
 };
 int top = 0, bottom = 2;
 int left = 0, right = 4;
 solve(matrix, top, bottom, left, right);
 return0;
}

Output

1 2 3 4 5 6 7 20 25 24 15 16 17 18 19

Python

defsolve(matrix, top, bottom, left, right):
 if left > right:
 return
 # print top row
 for i in range(left, right + 1):
 print(matrix[top][i], end=' ')
 top = top + 1
 if top > bottom:
 return
 # print right column
 for i in range(top, bottom + 1):
 print(matrix[i][right], end=' ')
 right = right - 1
 if left > right:
 return
 # print bottom row
 for i in range(right, left - 1, -1):
 print(matrix[bottom][i], end=' ')
 bottom = bottom - 1
 if top > bottom:
 return
 # print left column
 for i in range(bottom, top - 1, -1):
 print(matrix[i][left], end=' ')
 left = left + 1
 solve(matrix, top, bottom, left, right)
matrix = [
 [1, 2, 3, 4, 5],
 [16, 17, 18, 19, 6],
 [15, 24, 25, 20, 7]
]
top = 0
bottom = len(matrix) - 1
left = 0
right = len(matrix[0]) - 1
solve(matrix, top, bottom, left, right)

Output

1 2 3 4 5 6 7 20 25 24 15 16 17 18 19

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