# Program to print double headed arrow pattern

Given an integer N which is the number of rows, the task is to draw the number pattern in the shape of a double headed arrow.

Prerequisite: The pattern is a grow and shrink type pattern and hence basic knowledge to execute loops is required to understand the topic and the code in any language. The geometric shape can be visualized as- Examples:

```Input: R = 7
Output:
1
2 1 1 2
3 2 1   1 2 3
4 3 2 1     1 2 3 4
3 2 1   1 2 3
2 1 1 2
1

Input: R = 9
Output:
1
2 1 1 2
3 2 1   1 2 3
4 3 2 1     1 2 3 4
5 4 3 2 1       1 2 3 4 5
4 3 2 1     1 2 3 4
3 2 1   1 2 3
2 1 1 2
1
```

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

Approach:

1. In the given example, N=7 and the number of ROWS is 7.
2. VERTICALLY, the pattern GROWS till ROW=N/2 and SHRINKS afterwards.
3. ROW 1 has 4 ” “(SPACE) characters and then a value.
4. The number of SPACE characters decreases whereas NUMERALS increase in count in each successive row.
5. Also, note that the 1st value of the number placed in each row is the same as the number of the row.
6. Also HORIZONTALLY the pattern has NUMERALS, then SPACES and NUMERALS afterwards.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach ` `#include ` `using` `namespace` `std; ` ` `  `// Function to print the requried pattern ` `void` `drawPattern(``int` `N) ` `{ ` `    ``int` `n = N; ` `    ``int` `row = 1; ` ` `  `    ``// 'nst' is the number of values ` `    ``int` `nst = 1; ` ` `  `    ``// 'nsp' is the number of spaces ` `    ``int` `nsp1 = n - 1; ` `    ``int` `nsp2 = -1; ` `    ``int` `val1 = row; ` `    ``int` `val2 = 1; ` ` `  `    ``while` `(row <= n) { ` ` `  `        ``// Here spaces are printed ` `        ``// 'csp' is the count of spaces ` `        ``int` `csp1 = 1; ` `        ``while` `(csp1 <= nsp1) { ` `            ``cout << ``" "` `                 ``<< ``" "``; ` `            ``csp1 = csp1 + 1; ` `        ``} ` ` `  `        ``// Now, values are printed ` `        ``// 'cst' is the count of stars ` `        ``int` `cst1 = 1; ` `        ``while` `(cst1 <= nst) { ` `            ``cout << val1 << ``" "``; ` `            ``val1 = val1 - 1; ` `            ``cst1 = cst1 + 1; ` `        ``} ` ` `  `        ``// Again spaces have to be printed ` `        ``int` `csp2 = 1; ` `        ``while` `(csp2 <= nsp2) { ` `            ``cout << ``" "` `                 ``<< ``" "``; ` `            ``csp2 = csp2 + 1; ` `        ``} ` ` `  `        ``// Again values have to be printed ` `        ``if` `(row != 1 && row != n) { ` `            ``int` `cst2 = 1; ` `            ``while` `(cst2 <= nst) { ` `                ``cout << val2 << ``" "``; ` `                ``val2 = val2 + 1; ` `                ``cst2 = cst2 + 1; ` `            ``} ` `        ``} ` `        ``cout << endl; ` ` `  `        ``// Move to the next row ` `        ``if` `(row <= n / 2) { ` `            ``nst = nst + 1; ` `            ``nsp1 = nsp1 - 2; ` `            ``nsp2 = nsp2 + 2; ` `            ``val1 = row + 1; ` `            ``val2 = 1; ` `        ``} ` `        ``else` `{ ` `            ``nst = nst - 1; ` `            ``nsp1 = nsp1 + 2; ` `            ``nsp2 = nsp2 - 2; ` `            ``val1 = n - row; ` `            ``val2 = 1; ` `        ``} ` `        ``row = row + 1; ` `    ``} ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``// Number of rows ` `    ``int` `N = 7; ` ` `  `    ``drawPattern(N); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java implementation of the approach ` `class` `GFG { ` ` `  `    ``// Function to print the requried pattern ` `    ``static` `void` `drawPattern(``int` `N) ` `    ``{ ` `        ``int` `n = N; ` `        ``int` `row = ``1``; ` ` `  `        ``// 'nst' is the number of values ` `        ``int` `nst = ``1``; ` ` `  `        ``// 'nsp' is the number of spaces ` `        ``int` `nsp1 = n - ``1``; ` `        ``int` `nsp2 = -``1``; ` `        ``int` `val1 = row; ` `        ``int` `val2 = ``1``; ` ` `  `        ``while` `(row <= n) { ` ` `  `            ``// Here spaces are printed ` `            ``// 'csp' is the count of spaces ` `            ``int` `csp1 = ``1``; ` `            ``while` `(csp1 <= nsp1) { ` `                ``System.out.print(``"  "``); ` `                ``csp1 = csp1 + ``1``; ` `            ``} ` ` `  `            ``// Now, values are printed ` `            ``// 'cst' is the count of stars ` `            ``int` `cst1 = ``1``; ` `            ``while` `(cst1 <= nst) { ` `                ``System.out.print(val1 + ``" "``); ` `                ``val1 = val1 - ``1``; ` `                ``cst1 = cst1 + ``1``; ` `            ``} ` ` `  `            ``// Again spaces have to be printed ` `            ``int` `csp2 = ``1``; ` `            ``while` `(csp2 <= nsp2) { ` `                ``System.out.print(``"  "``); ` `                ``csp2 = csp2 + ``1``; ` `            ``} ` ` `  `            ``// Again values have to be printed ` `            ``if` `(row != ``1` `&& row != n) { ` `                ``int` `cst2 = ``1``; ` `                ``while` `(cst2 <= nst) { ` `                    ``System.out.print(val2 + ``" "``); ` `                    ``val2 = val2 + ``1``; ` `                    ``cst2 = cst2 + ``1``; ` `                ``} ` `            ``} ` `            ``System.out.println(); ` ` `  `            ``// Move to the next row ` `            ``if` `(row <= n / ``2``) { ` `                ``nst = nst + ``1``; ` `                ``nsp1 = nsp1 - ``2``; ` `                ``nsp2 = nsp2 + ``2``; ` `                ``val1 = row + ``1``; ` `                ``val2 = ``1``; ` `            ``} ` `            ``else` `{ ` `                ``nst = nst - ``1``; ` `                ``nsp1 = nsp1 + ``2``; ` `                ``nsp2 = nsp2 - ``2``; ` `                ``val1 = n - row; ` `                ``val2 = ``1``; ` `            ``} ` `            ``row = row + ``1``; ` `        ``} ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `        ``// Number of rows ` `        ``int` `N = ``7``; ` ` `  `        ``drawPattern(N); ` `    ``} ` `} `

## Python3

 `# Python3 implementation of the approach  ` ` `  `# Function to print the requried pattern  ` `def` `drawPattern(N) :  ` ` `  `    ``n ``=` `N;  ` `    ``row ``=` `1``;  ` ` `  `    ``# 'nst' is the number of values  ` `    ``nst ``=` `1``;  ` ` `  `    ``# 'nsp' is the number of spaces  ` `    ``nsp1 ``=` `n ``-` `1``;  ` `    ``nsp2 ``=` `-``1``;  ` `    ``val1 ``=` `row;  ` `    ``val2 ``=` `1``;  ` ` `  `    ``while` `(row <``=` `n) : ` ` `  `        ``# Here spaces are printed  ` `        ``# 'csp' is the count of spaces  ` `        ``csp1 ``=` `1``;  ` `        ``while` `(csp1 <``=` `nsp1) : ` `            ``print``(``" "``,end``=` `" "``); ` `            ``csp1 ``=` `csp1 ``+` `1``;  ` ` `  `        ``# Now, values are printed  ` `        ``# 'cst' is the count of stars  ` `        ``cst1 ``=` `1``;  ` `        ``while` `(cst1 <``=` `nst) : ` `            ``print``(val1,end ``=` `" "``);  ` `            ``val1 ``=` `val1 ``-` `1``;  ` `            ``cst1 ``=` `cst1 ``+` `1``;  ` ` `  `        ``# Again spaces have to be printed  ` `        ``csp2 ``=` `1``;  ` `        ``while` `(csp2 <``=` `nsp2) : ` `            ``print``(``" "``,end ``=` `" "``);  ` `            ``csp2 ``=` `csp2 ``+` `1``;  ` ` `  `        ``# Again values have to be printed  ` `        ``if` `(row !``=` `1` `and` `row !``=` `n) : ` `            ``cst2 ``=` `1``;  ` `             `  `            ``while` `(cst2 <``=` `nst) : ` `                ``print``(val2,end ``=` `" "``);  ` `                ``val2 ``=` `val2 ``+` `1``;  ` `                ``cst2 ``=` `cst2 ``+` `1``;  ` `         `  `        ``print``() ` ` `  `        ``# Move to the next row  ` `        ``if` `(row <``=` `n ``/``/` `2``) : ` `            ``nst ``=` `nst ``+` `1``;  ` `            ``nsp1 ``=` `nsp1 ``-` `2``;  ` `            ``nsp2 ``=` `nsp2 ``+` `2``;  ` `            ``val1 ``=` `row ``+` `1``;  ` `            ``val2 ``=` `1``;  ` ` `  `        ``else` `: ` `            ``nst ``=` `nst ``-` `1``;  ` `            ``nsp1 ``=` `nsp1 ``+` `2``;  ` `            ``nsp2 ``=` `nsp2 ``-` `2``;  ` `            ``val1 ``=` `n ``-` `row;  ` `            ``val2 ``=` `1``;  ` `         `  `        ``row ``=` `row ``+` `1``;  ` ` `  `# Driver code  ` `if` `__name__ ``=``=` `"__main__"` `:  ` ` `  `    ``# Number of rows  ` `    ``N ``=` `7``;  ` ` `  `    ``drawPattern(N);  ` ` `  `# This code is contributed by AnkitRai01 `

## C#

 `// C# implementation of the approach ` `using` `System; ` ` `  `class` `GFG  ` `{ ` ` `  `    ``// Function to print the requried pattern ` `    ``static` `void` `drawPattern(``int` `N) ` `    ``{ ` `        ``int` `n = N; ` `        ``int` `row = 1; ` ` `  `        ``// 'nst' is the number of values ` `        ``int` `nst = 1; ` ` `  `        ``// 'nsp' is the number of spaces ` `        ``int` `nsp1 = n - 1; ` `        ``int` `nsp2 = -1; ` `        ``int` `val1 = row; ` `        ``int` `val2 = 1; ` ` `  `        ``while` `(row <= n)  ` `        ``{ ` ` `  `            ``// Here spaces are printed ` `            ``// 'csp' is the count of spaces ` `            ``int` `csp1 = 1; ` `            ``while` `(csp1 <= nsp1) ` `            ``{ ` `                ``Console.Write(``" "``); ` `                ``csp1 = csp1 + 1; ` `            ``} ` ` `  `            ``// Now, values are printed ` `            ``// 'cst' is the count of stars ` `            ``int` `cst1 = 1; ` `            ``while` `(cst1 <= nst)  ` `            ``{ ` `                ``Console.Write(val1 + ``" "``); ` `                ``val1 = val1 - 1; ` `                ``cst1 = cst1 + 1; ` `            ``} ` ` `  `            ``// Again spaces have to be printed ` `            ``int` `csp2 = 1; ` `            ``while` `(csp2 <= nsp2)  ` `            ``{ ` `                ``Console.Write(``" "``); ` `                ``csp2 = csp2 + 1; ` `            ``} ` ` `  `            ``// Again values have to be printed ` `            ``if` `(row != 1 && row != n) ` `            ``{ ` `                ``int` `cst2 = 1; ` `                ``while` `(cst2 <= nst)  ` `                ``{ ` `                    ``Console.Write(val2 + ``" "``); ` `                    ``val2 = val2 + 1; ` `                    ``cst2 = cst2 + 1; ` `                ``} ` `            ``} ` `            ``Console.WriteLine(); ` ` `  `            ``// Move to the next row ` `            ``if` `(row <= n / 2) ` `            ``{ ` `                ``nst = nst + 1; ` `                ``nsp1 = nsp1 - 2; ` `                ``nsp2 = nsp2 + 2; ` `                ``val1 = row + 1; ` `                ``val2 = 1; ` `            ``} ` `            ``else`  `            ``{ ` `                ``nst = nst - 1; ` `                ``nsp1 = nsp1 + 2; ` `                ``nsp2 = nsp2 - 2; ` `                ``val1 = n - row; ` `                ``val2 = 1; ` `            ``} ` `            ``row = row + 1; ` `        ``} ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `Main() ` `    ``{ ` `        ``// Number of rows ` `        ``int` `N = 7; ` ` `  `        ``drawPattern(N); ` `    ``} ` `} ` ` `  `// This code is contributed by AnkitRai01 `

Output:

```            1
2 1   1 2
3 2 1       1 2 3
4 3 2 1           1 2 3 4
3 2 1       1 2 3
2 1   1 2
1
```

Time Complexity: O(N2)
Space Complexity: O(1)

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