Monotone Increasing Digits in C++

C++Server Side ProgrammingProgramming

Suppose we have a non-negative integer N, we have to find the largest number that is less than or equal to N with monotone increasing digits. We know that an integer has monotone increasing digits if and only if each pair of adjacent digits’ x and y satisfy x <= y.) So if the input is like 332, then the result will be 299.

To solve this, we will follow these steps −

  • s := N as string, i := 1, n := size of s
  • while i < n and s[i] >= s[i – 1]
    • increase i by 1
  • if i < n
    • while i > 0 and s[i – 1] > s[i], then
      • decrease i by 1
      • decrease s[i] by 1
  • for j in range i + 1 to n
    • s[j] := ‘9’
  • return s as number

Let us see the following implementation to get better understanding −

Example

 Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
public:
   int monotoneIncreasingDigits(int N) {
      string s = to_string(N);
      int i = 1;
      int n = s.size();
      while(i < n && s[i] >= s[i - 1]) i++;
      if( i < n)
      while(i > 0 && s[i - 1] > s[i]){
         i--;
         s[i]--;
      }
      for(int j = i + 1; j < n; j++)s[j] = '9';
      return stoi(s);
   }
};
main(){
   Solution ob;
   cout << (ob.monotoneIncreasingDigits(332));
}

Input

332

Output

299
raja
Published on 04-May-2020 13:45:38
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