Given a number **d**, representing the number of digits of a positive integer. Find the total count of positive integer (consisting of d digits exactly) which have at-least one zero in them.

Examples:

Input : d = 1 Output : 0 There's no natural number of 1 digit that contains a zero. Input : d = 2 Output : 9 The numbers are, 10, 20, 30, 40, 50, 60, 70, 80 and 90.

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One Simple Solution is to traverse through all d digit positive numbers. For every number, traverse through its digits and if there is any 0 digit, increment count (similar to this).

Following are some observations:

- There are exactly d digits.
- The number at most significant place can’t be a zero (no leading zeroes allowed).
- All the other places except the most significant one can contain zero .

So considering the above points, let’s find the total count of numbers having d digits:

We can place any of {1, 2, ... 9} in D1 Hence D1 can be filled in 9 ways. Apart from D1 all the other places can be 10 ways. (we can place 0 as well) Hence the total numbers having d digits can be given as:Total = 9*10Now, let's find the numbers having d digits, that don't contain zero at any place. In this case, all the places can be filled in 9 ways. Hence count of such numbers is given by:^{d-1}Non_Zero = 9Now the count of numbers having at least one zero can be obtained by subtracting Non_Zero from Total. Hence Answer would be given by:^{d}9*(10^{d-1}- 9^{d-1})

Below is the program for the same.

`//C++ program to find the count of positive integer of a ` `// given number of digits that contain atleast one zero ` `#include<bits/stdc++.h> ` `using` `namespace` `std; `
` ` `// Returns count of 'd' digit integers have 0 as a digit ` `int` `findCount(` `int` `d) `
`{ ` ` ` `return` `9*(` `pow` `(10,d-1) - ` `pow` `(9,d-1)); `
`} ` ` ` `// Driver Code ` `int` `main() `
`{ ` ` ` `int` `d = 1; `
` ` `cout << findCount(d) << endl; `
` ` ` ` `d = 2; `
` ` `cout << findCount(d) << endl; `
` ` ` ` `d = 4; `
` ` `cout << findCount(d) << endl; `
` ` `return` `0; `
`} ` |

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`// Java program to find the count ` `// of positive integer of a ` `// given number of digits ` `// that contain atleast one zero ` `import` `java.io.*; `
` ` `class` `GFG { `
` ` ` ` `// Returns count of 'd' digit `
` ` `// integers have 0 as a digit `
` ` `static` `int` `findCount(` `int` `d) `
` ` `{ `
` ` `return` `9` `* ((` `int` `)(Math.pow(` `10` `, d - ` `1` `)) `
` ` `- (` `int` `)(Math.pow(` `9` `, d - ` `1` `))); `
` ` `} `
` ` ` ` `// Driver Code `
` ` `public` `static` `void` `main(String args[]) `
` ` `{ `
` ` `int` `d = ` `1` `; `
` ` `System.out.println(findCount(d)); `
` ` ` ` `d = ` `2` `; `
` ` `System.out.println(findCount(d)); `
` ` ` ` `d = ` `4` `; `
` ` `System.out.println(findCount(d)); `
` ` ` ` `} `
`} ` ` ` `// This code is contributed by Nikita Tiwari. ` |

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`# Python 3 program to find the ` `# count of positive integer of a ` `# given number of digits that ` `# contain atleast one zero ` `import` `math `
` ` `# Returns count of 'd' digit ` `# integers have 0 as a digit ` `def` `findCount(d) : `
` ` `return` `9` `*` `((` `int` `)(math.` `pow` `(` `10` `,d` `-` `1` `)) ` `-` `(` `int` `)(math.` `pow` `(` `9` `,d` `-` `1` `))); `
` ` ` ` `# Driver Code ` `d ` `=` `1`
`print` `(findCount(d)) `
` ` `d ` `=` `2`
`print` `(findCount(d)) `
` ` `d ` `=` `4`
`print` `(findCount(d)) `
` ` ` ` `# This code is contributed by Nikita Tiwari. ` |

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`// C# program to find the count ` `// of positive integer of a ` `// given number of digits ` `// that contain atleast one zero. ` `using` `System; `
` ` `class` `GFG { `
` ` ` ` `// Returns count of 'd' digit `
` ` `// integers have 0 as a digit `
` ` `static` `int` `findCount(` `int` `d) `
` ` `{ `
` ` `return` `9 * ((` `int` `)(Math.Pow(10, d - 1)) `
` ` `- (` `int` `)(Math.Pow(9, d - 1))); `
` ` `} `
` ` ` ` `// Driver Code `
` ` `public` `static` `void` `Main() `
` ` `{ `
` ` `int` `d = 1; `
` ` `Console.WriteLine(findCount(d)); `
` ` ` ` `d = 2; `
` ` `Console.WriteLine(findCount(d)); `
` ` ` ` `d = 4; `
` ` `Console.WriteLine(findCount(d)); `
` ` ` ` `} `
`} ` ` ` `// This code is contributed by nitin mittal. ` |

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`<?php ` `// PHP program to find the count ` `// of positive integer of a given ` `// number of digits that contain ` `// atleast one zero ` ` ` `// Returns count of 'd' digit ` `// integers have 0 as a digit ` `function` `findCount(` `$d` `) `
`{ ` ` ` `return` `9 * (pow(10, ` `$d` `- 1) - `
` ` `pow(9, ` `$d` `- 1)); `
`} ` ` ` `// Driver Code ` `{ ` ` ` `$d` `= 1; `
` ` `echo` `findCount(` `$d` `),` `"\n"` `; `
` ` ` ` `$d` `= 2; `
` ` `echo` `findCount(` `$d` `),` `"\n"` `; `
` ` ` ` `$d` `= 4; `
` ` `echo` `findCount(` `$d` `), ` `"\n"` `; `
` ` `return` `0; `
`} ` ` ` `// This code is contributed by nitin mittal ` `?> ` |

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Output :

0 9 2439

This article is contributed by Ashutosh Kumar. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

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