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Find the closest and smaller tidy number
  • Difficulty Level : Easy
  • Last Updated : 07 May, 2021

Tidy Number are those number whose digits are arranged in non-decreasing order. Here, we are given a number and we have to find another number that is smaller but closest to the given number and also that number should be tidy, i.e., their digit should be in non-decreasing order. 

Examples: 

Input  : 91234
Output : 89999
Tidy property is violated by appearing 1 after 9. 
So, we will reduce 9 by 1 and the number right
to it will be replaced by 9. So, generated tidy
number is 89999.

Input  : 45000
Output : 44999

The idea is to traverse from end. Whenever tidy property is violated, we reduce digit by one and make all subsequent digits 9.  

C++




// C++ program to find closest
// tidy number smaller than the
// given number
#include<bits/stdc++.h>
using namespace std;
 
char* tidyNum(char str[], int len)
{
    for (int i = len-2; i >= 0; i--)
    {
        // check whether string violates tidy property
        if (str[i] > str[i+1])
        {
            // if string violates tidy property, then
            // decrease the value stored at that index by 1
            // and replace all the value stored right to
            // that index by 9
            (char)str[i]--;
            for (int j=i+1; j<len; j++)
                str[j] = '9';
        }
    }
    return str;
}
 
// Driver code
int main()
{
    char str[] = "11333445538";
    int len = strlen(str);
     
    // num will store closest tidy number
    char *num = tidyNum(str, len);
    printf("%s\n", num);
    return 0;
}

Java




// Java program to find closest
// tidy number smaller than the
// given number
import java.io.*;
class GFG
{
static String tidyNum(String str1,
                      int len)
{
    char[] str = str1.toCharArray();
    for (int i = len - 2; i >= 0; i--)
    {
        // check whether string
        // violates tidy property
        if (str[i] > str[i + 1])
        {
            // if string violates tidy
            // property, then decrease the
            // value stored at that index
            // by 1 and replace all the value
            // stored right to that index by 9
            str[i]--;
            for (int j = i + 1; j < len; j++)
                str[j] = '9';
        }
    }
    return String.valueOf(str);
}
 
// Driver code
public static void main(String[] args)
{
    String str = "11333445538";
    int len = str.length();
     
    // num will store closest tidy number
    System.out.println(tidyNum(str, len));
}
}
 
// This code is contributed by mits

Python3




# Python 3 program to find closest
# tidy number smaller than the
# given number
 
def tidyNum(str, len):
 
    for i in range(len-2, -1, -1):
     
        # check whether string
        # violates tidy property
        if (str[i] > str[i+1]):
         
            # if string violates tidy
            # property, then decrease the
            # value stored at that index by 1
            # and replace all the value
            # stored right to that index by 9
            str[i] -= 1
            for j in range(i+1, len):
                str[j] = 9
         
    return str
 
# Driver code
str = [1,1,3,3,3,4,4,5,5,3,8]
len = len(str)
     
# num will store closest tidy number
num = tidyNum(str, len)
 
for i in range(0,len):
    print(str[i], end = "")
 
# This code is contributed by
# Smitha Dinesh Semwal

C#




// C# program to find closest
// tidy number smaller than the
// given number
using System;
 
class GFG
{
static String tidyNum(String str1, int len)
{
    char[] str = str1.ToCharArray();
    for (int i = len - 2; i >= 0; i--)
    {
        // check whether string
        // violates tidy property
        if (str[i] > str[i + 1])
        {
            // if string violates tidy
            // property, then decrease the
            // value stored at that index
            // by 1 and replace all the value
            // stored right to that index by 9
            str[i]--;
            for (int j = i + 1; j < len; j++)
                str[j] = '9';
        }
    }
    string s = new string(str);
    return s;
}
 
// Driver code
static void Main()
{
    String str = "11333445538";
    int len = str.Length;
     
    // num will store closest tidy number
    Console.WriteLine(tidyNum(str, len));
}
}
 
// This code is contributed by mits

PHP




<?php
// PHP program to find closest
// tidy number smaller than the
// given number
 
function tidyNum($str, $len)
{
    for ($i = $len - 2; $i >= 0; $i--)
    {
        // check whether string
        // violates tidy property
        if ($str[$i] > $str[$i + 1])
        {
            // if string violates tidy
            // property, then decrease
            // the value stored at that
            // index by 1 and replace all
            // the value stored right to
            // that index by 9
            $x = ord($str[$i]);
            $x--;
            $str[$i] = chr($x);
            for ($j = $i + 1; $j < $len; $j++)
                $str[$j] = '9';
        }
    }
    return $str;
}
 
// Driver code
$str = "11333445538";
$len = strlen($str);
 
// num will store
// closest tidy number
$num = tidyNum($str, $len);
echo $num;
 
// This code is contributed by mits
?>

Javascript




<script>
 
// Javascript program to find closest
// tidy number smaller than the
// given number
function tidyNum(str1, len)
{
    var str = str1.split('');
    for (i = len - 2; i >= 0; i--)
    {
         
        // Check whether string
        // violates tidy property
        if (str[i] > str[i + 1])
        {
             
            // If string violates tidy
            // property, then decrease the
            // value stored at that index
            // by 1 and replace all the value
            // stored right to that index by 9
            str[i]--;
             
            for(j = i + 1; j < len; j++)
                str[j] = '9';
        }
    }
    return str.join("");
}
 
// Driver code
var str = "11333445538";
var len = str.length;
 
// num will store closest tidy number
document.write(tidyNum(str, len));
 
// This code is contributed by Amit Katiyar
 
</script>

Output: 

11333444999

References :
This question is asked in Google Code Jam 2017 qualification round.

This article is contributed by Aditya kumar. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.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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