# 9’s complement of a decimal number

9’s complement of a decimal number is the subtraction of it’s each digits from 9. Like 1’s complement, 9’s complement is used to subtract a number using addition.

For example, let us compute value of “718 – 123” using 9’s complement and addition. We first find 9’s complement of 718 which is 281. Now we add 281 to 123. We get 404. 9’s complement of this is 595 which is equal to “718 – 123”. So we could find subtraction using addition and 9’s complement.

In case while adding a carry is obtained in the end, also known as the end around carry, it should be added to the answer, removing the carry itself. For example, (83-25) , 9’s complement of 25 is 74 and (83+74 = 157). A carry is obtained, now add it to the number 57, (57+1 = 58) which is the answer.

Given a decimal number n, find 9’s complement of the number.

Input : 25 Output : 9's complement is : 74 Input : 345.45 Output : 9's complement is : 654.54

Let the number be stored as string. We traverse digits of number and subtract every digit from 9.

## C++

`// C++ program to find 9's complement of a` `// number.` `#include<iostream>` `using` `namespace` `std;` `void` `complement(string number)` `{` ` ` `for` `(` `int` `i=0 ; i < number.length() ; i++ )` ` ` `if` `(number[i] != ` `'.'` `)` ` ` `number[i] = ` `'9'` `- number[i] + ` `'0'` `;` ` ` `cout << ` `"9's complement is : "` `<< number;` `}` `// Driver code` `int` `main()` `{` ` ` `string number = ` `"345.45"` `;` ` ` `complement(number);` ` ` `return` `0;` `}` |

## Java

`// Java program to find 9's complement of a` `// number.` `class` `GFG{` `static` `void` `complement(String number1)` `{` ` ` `char` `[] number=number1.toCharArray();` ` ` `for` `(` `int` `i=` `0` `; i < number.length ; i++ )` ` ` `if` `(number[i] != ` `'.'` `)` ` ` `number[i] = (` `char` `)((` `int` `)(` `'9'` `) - (` `int` `)(number[i]) + (` `int` `)(` `'0'` `));` ` ` `System.out.println( ` `"9's complement is : "` `+String.valueOf(number));` `}` `// Driver code` `public` `static` `void` `main(String[] args)` `{` ` ` `String number = ` `"345.45"` `;` ` ` `complement(number);` `}` `}` `//This code is contributed by mits` |

## Python3

`# Python3 program to find 9's` `# complement of a number.` `def` `complement(number):` ` ` `for` `i ` `in` `range` `(` `0` `, ` `len` `(number)):` ` ` `if` `(number[i] !` `=` `'.'` `):` ` ` `a ` `=` `9` `-` `int` `(number[i])` ` ` `number ` `=` `(number[:i] ` `+` ` ` `str` `(a) ` `+` `number[i ` `+` `1` `:])` ` ` `print` `(` `"9's complement is : "` `, number)` `# Driver code` `if` `__name__` `=` `=` `'__main__'` `:` ` ` `number ` `=` `"345.45"` ` ` `complement(number)` `# This code is contributed by` `# Sanjit_Prasad` |

## C#

`// C# program to find 9's complement of a` `// number.` `using` `System;` `class` `GFG{` `static` `void` `complement(` `string` `number1)` `{` ` ` `char` `[] number=number1.ToCharArray();` ` ` `for` `(` `int` `i=0 ; i < number.Length ; i++ )` ` ` `if` `(number[i] != ` `'.'` `)` ` ` `number[i] = (` `char` `)((` `int` `)(` `'9'` `) -` ` ` `(` `int` `)(number[i]) + (` `int` `)(` `'0'` `));` ` ` `System.Console.WriteLine( ` `"9's complement is : "` ` ` `+` `new` `string` `(number));` `}` `// Driver code` `public` `static` `void` `Main()` `{` ` ` `String number = ` `"345.45"` `;` ` ` `complement(number);` `}` `}` `//This code is contributed by mits` |

## PHP

`<?php` `// PHP program to find 9's complement of a` `// number.` `function` `complement( ` `$number` `)` `{` ` ` `for` `( ` `$i` `=0 ; ` `$i` `< ` `strlen` `(` `$number` `) ; ` `$i` `++ )` ` ` `if` `(` `$number` `[` `$i` `] != ` `'.'` `)` ` ` `$number` `[` `$i` `] = ` `'9'` `- ` `$number` `[` `$i` `] + ` `'0'` `;` ` ` `echo` `"9's complement is : "` `, ` `$number` `;` `}` `// Driver code` ` ` `$number` `= ` `"345.45"` `;` ` ` `complement(` `$number` `);` `// This code is contributed by anuj_67.` `?>` |

## Javascript

`<script>` `// Javascript program to find 9's complement of a` `// number.` `function` `complement(number)` `{` ` ` `number = number.split('` `')` ` ` `for (let i=0 ; i < number.length; i++ ){ ` ` ` `if (number[i] != '` `.` `'){` ` ` `number[i] = String(9 - Number(number[i]) + 0);` ` ` `}` ` ` `}` ` ` `number = number.join("")` ` ` `document.write("9'` `s complement is : " + number);` `}` `// Driver code` ` ` `let number = ` `"345.45"` `;` ` ` `complement(number);` `// This code is contributed by gfgking.` `</script>` |

**Output:**

9's complement is : 654.54

This article is contributed by **Dibyendu Roy Chaudhuri**. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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