# Form a Spiral Matrix from the given Array

Given an array, the task is to form a spiral matrix

Examples:

```Input:
arr[] = { 1, 2, 3, 4, 5,
6, 7, 8, 9, 10,
11, 12, 13, 14, 15, 16 };
Output:
1  2  3  4
12 13 14  5
11 16 15  6
10  9  8  7

Input:
arr[] = { 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 11, 12,
13, 14, 15, 16, 17, 18 };
Output:
1   2  3  4  5 6
14 15 16 17 18 7
13 12 11 10  9 8
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: This problem is just the reverse of this problem “Print a given matrix in spiral form“. The approach to do so is:

• Traverse the given array and pick each element one by one.
• Fill each of this element in the spiral matrix order.
• Spiral matrix order is maintained with the help of 4 loops – left, right, top, and bottom.
• Each loop prints its corresponding row/column in the spiral matrix.

Below is the implementation of the above approach:

## C++

 `// C++ program to form a Spiral Matrix ` `// from the given Array ` ` `  `#include ` `using` `namespace` `std; ` ` `  `#define R 3 ` `#define C 6 ` ` `  `// Function to form the spiral matrix ` `void` `formSpiralMatrix(``int` `arr[], ``int` `mat[R][C]) ` `{ ` `    ``int` `top = 0, ` `        ``bottom = R - 1, ` `        ``left = 0, ` `        ``right = C - 1; ` ` `  `    ``int` `index = 0; ` ` `  `    ``while` `(1) { ` ` `  `        ``if` `(left > right) ` `            ``break``; ` ` `  `        ``// print top row ` `        ``for` `(``int` `i = left; i <= right; i++) ` `            ``mat[top][i] = arr[index++]; ` `        ``top++; ` ` `  `        ``if` `(top > bottom) ` `            ``break``; ` ` `  `        ``// print right column ` `        ``for` `(``int` `i = top; i <= bottom; i++) ` `            ``mat[i][right] = arr[index++]; ` `        ``right--; ` ` `  `        ``if` `(left > right) ` `            ``break``; ` ` `  `        ``// print bottom row ` `        ``for` `(``int` `i = right; i >= left; i--) ` `            ``mat[bottom][i] = arr[index++]; ` `        ``bottom--; ` ` `  `        ``if` `(top > bottom) ` `            ``break``; ` ` `  `        ``// print left column ` `        ``for` `(``int` `i = bottom; i >= top; i--) ` `            ``mat[i][left] = arr[index++]; ` `        ``left++; ` `    ``} ` `} ` ` `  `// Function to print the spiral matrix ` `void` `printSpiralMatrix(``int` `mat[R][C]) ` `{ ` ` `  `    ``for` `(``int` `i = 0; i < R; i++) { ` `        ``for` `(``int` `j = 0; j < C; j++) ` `            ``cout << mat[i][j] << ``" "``; ` `        ``cout << ``'\n'``; ` `    ``} ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `arr[] ` `        ``= { 1, 2, 3, 4, 5, 6, ` `            ``7, 8, 9, 10, 11, 12, ` `            ``13, 14, 15, 16, 17, 18 }; ` `    ``int` `mat[R][C]; ` ` `  `    ``formSpiralMatrix(arr, mat); ` `    ``printSpiralMatrix(mat); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java program to form a Spiral Matrix  ` `// from the given Array  ` `class` `GFG  ` `{ ` `    ``static` `final` `int` `R = ``3` `; ` `    ``static` `final` `int` `C = ``6``;  ` ` `  `    ``// Function to form the spiral matrix  ` `    ``static` `void` `formSpiralMatrix(``int` `arr[], ``int` `mat[][])  ` `    ``{  ` `        ``int` `top = ``0``,  ` `            ``bottom = R - ``1``,  ` `            ``left = ``0``,  ` `            ``right = C - ``1``;  ` `     `  `        ``int` `index = ``0``;  ` `     `  `        ``while` `(``true``)  ` `        ``{  ` `            ``if` `(left > right)  ` `                ``break``;  ` `     `  `            ``// print top row  ` `            ``for` `(``int` `i = left; i <= right; i++)  ` `                ``mat[top][i] = arr[index++];  ` `            ``top++;  ` `     `  `            ``if` `(top > bottom)  ` `                ``break``;  ` `     `  `            ``// print right column  ` `            ``for` `(``int` `i = top; i <= bottom; i++)  ` `                ``mat[i][right] = arr[index++];  ` `            ``right--;  ` `     `  `            ``if` `(left > right)  ` `                ``break``;  ` `     `  `            ``// print bottom row  ` `            ``for` `(``int` `i = right; i >= left; i--)  ` `                ``mat[bottom][i] = arr[index++];  ` `            ``bottom--;  ` `     `  `            ``if` `(top > bottom)  ` `                ``break``;  ` `     `  `            ``// print left column  ` `            ``for` `(``int` `i = bottom; i >= top; i--)  ` `                ``mat[i][left] = arr[index++];  ` `            ``left++;  ` `        ``}  ` `    ``}  ` `     `  `    ``// Function to print the spiral matrix  ` `    ``static` `void` `printSpiralMatrix(``int` `mat[][])  ` `    ``{  ` `        ``for` `(``int` `i = ``0``; i < R; i++) ` `        ``{  ` `            ``for` `(``int` `j = ``0``; j < C; j++)  ` `                ``System.out.print(mat[i][j] + ``" "``);  ` `            ``System.out.println();  ` `        ``}  ` `    ``}  ` `     `  `    ``// Driver code  ` `    ``public` `static` `void` `main (String[] args) ` `    ``{  ` `        ``int` `arr[] = { ``1``, ``2``, ``3``, ``4``, ``5``, ``6``,  ` `                      ``7``, ``8``, ``9``, ``10``, ``11``, ``12``,  ` `                      ``13``, ``14``, ``15``, ``16``, ``17``, ``18` `};  ` `                 `  `        ``int` `mat[][] = ``new` `int``[R][C];  ` `     `  `        ``formSpiralMatrix(arr, mat);  ` `        ``printSpiralMatrix(mat);  ` `    ``}  ` `} ` ` `  `// This code is contributed by kanugargng `

## Python3

 `# Python program to form a Spiral Matrix  ` `# from the given Array  ` ` `  `R ``=` `3` `; ` `C ``=` `6``;  ` ` `  `# Function to form the spiral matrix  ` `def` `formSpiralMatrix(arr, mat): ` `    ``top ``=` `0``; ` `    ``bottom ``=` `R ``-` `1``; ` `    ``left ``=` `0``;  ` `    ``right ``=` `C ``-` `1``;  ` ` `  `    ``index ``=` `0``;  ` ` `  `    ``while` `(``True``): ` `         `  `        ``if``(left > right):  ` `            ``break``;  ` ` `  `        ``# prtop row  ` `        ``for` `i ``in` `range``(left, right ``+` `1``): ` `            ``mat[top][i] ``=` `arr[index]; ` `            ``index ``+``=` `1``; ` `        ``top ``+``=` `1``;  ` ` `  `        ``if` `(top > bottom): ` `            ``break``;  ` ` `  `        ``# prright column  ` `        ``for` `i ``in` `range``(top, bottom``+``1``): ` `            ``mat[i][right] ``=` `arr[index]; ` `            ``index ``+``=` `1``; ` `        ``right ``-``=` `1``;  ` ` `  `        ``if` `(left > right): ` `            ``break``;  ` ` `  `        ``# prbottom row  ` `        ``for` `i ``in` `range``(right, left``-``1``, ``-``1``): ` `            ``mat[bottom][i] ``=` `arr[index]; ` `            ``index ``+``=` `1``; ` `        ``bottom ``-``=` `1``;  ` ` `  `        ``if` `(top > bottom):  ` `            ``break``;  ` ` `  `        ``# prleft column  ` `        ``for` `i ``in` `range``(bottom, top``-``1``, ``-``1``):  ` `            ``mat[i][left] ``=` `arr[index]; ` `            ``index ``+``=` `1``; ` `        ``left ``+``=` `1``;  ` `# Function to prthe spiral matrix  ` `def` `printSpiralMatrix(mat): ` `    ``for` `i ``in` `range``(R): ` `        ``for` `j ``in` `range``(C): ` `            ``print``(mat[i][j],end``=` `" "``);  ` `        ``print``();  ` ` `  `# Driver code  ` `if` `__name__ ``=``=` `'__main__'``: ` `    ``arr ``=` `[ ``1``, ``2``, ``3``, ``4``, ``5``, ``6``,  ` `                ``7``, ``8``, ``9``, ``10``, ``11``, ``12``,  ` `                ``13``, ``14``, ``15``, ``16``, ``17``, ``18` `];  ` ` `  `    ``mat``=` `[[``0` `for` `i ``in` `range``(C)] ``for` `j ``in` `range``(R)]; ` `    ``formSpiralMatrix(arr, mat);  ` `    ``printSpiralMatrix(mat);  ` ` `  `# This code contributed by PrinciRaj1992 `

## C#

 `// C# program to form a Spiral Matrix  ` `// from the given Array  ` `using` `System; ` `     `  `class` `GFG  ` `{ ` `    ``static` `readonly` `int` `R = 3; ` `    ``static` `readonly` `int` `C = 6;  ` ` `  `    ``// Function to form the spiral matrix  ` `    ``static` `void` `formSpiralMatrix(``int` `[]arr,  ` `                                 ``int` `[,]mat)  ` `    ``{  ` `        ``int` `top = 0,  ` `            ``bottom = R - 1,  ` `            ``left = 0,  ` `            ``right = C - 1;  ` `     `  `        ``int` `index = 0;  ` `     `  `        ``while` `(``true``)  ` `        ``{  ` `            ``if` `(left > right)  ` `                ``break``;  ` `     `  `            ``// print top row  ` `            ``for` `(``int` `i = left; i <= right; i++)  ` `                ``mat[top, i] = arr[index++];  ` `            ``top++;  ` `     `  `            ``if` `(top > bottom)  ` `                ``break``;  ` `     `  `            ``// print right column  ` `            ``for` `(``int` `i = top; i <= bottom; i++)  ` `                ``mat[i, right] = arr[index++];  ` `            ``right--;  ` `     `  `            ``if` `(left > right)  ` `                ``break``;  ` `     `  `            ``// print bottom row  ` `            ``for` `(``int` `i = right; i >= left; i--)  ` `                ``mat[bottom, i] = arr[index++];  ` `            ``bottom--;  ` `     `  `            ``if` `(top > bottom)  ` `                ``break``;  ` `     `  `            ``// print left column  ` `            ``for` `(``int` `i = bottom; i >= top; i--)  ` `                ``mat[i, left] = arr[index++];  ` `            ``left++;  ` `        ``}  ` `    ``}  ` `     `  `    ``// Function to print the spiral matrix  ` `    ``static` `void` `printSpiralMatrix(``int` `[,]mat)  ` `    ``{  ` `        ``for` `(``int` `i = 0; i < R; i++) ` `        ``{  ` `            ``for` `(``int` `j = 0; j < C; j++)  ` `                ``Console.Write(mat[i, j] + ``" "``);  ` `            ``Console.WriteLine();  ` `        ``}  ` `    ``}  ` `     `  `    ``// Driver code  ` `    ``public` `static` `void` `Main (String[] args) ` `    ``{  ` `        ``int` `[]arr = { 1, 2, 3, 4, 5, 6,  ` `                      ``7, 8, 9, 10, 11, 12,  ` `                     ``13, 14, 15, 16, 17, 18 };  ` `                 `  `        ``int` `[,]mat = ``new` `int``[R, C];  ` `     `  `        ``formSpiralMatrix(arr, mat);  ` `        ``printSpiralMatrix(mat);  ` `    ``}  ` `} ` ` `  `// This code is contributed by 29AjayKumar `

Output:

```1   2  3  4  5 6
14 15 16 17 18 7
13 12 11 10  9 8
```

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