Print all 3 digit repeating numbers in a very large number

Given a very large number, print all the 3 digit repeating numbers with their frequency. If a 3 digit number appears more then once, print the number and its frequency.

Example:

Input: 123412345123456
Output: 123 - 3 times
         234 - 3 times
         345 - 2 times 

Input: 43243243
Output: 432 - 2 times
        324 - 2 times
        243 - 2 times

Approach: Since the number is very large, it is stored in a string. Initially, the first three digit number will be the first three characters from the left. Iterate in the string from the 3rd index from the left in the string and do %100 to remove the first character and append the ith index number at the end to get the new number. Increase the frequency of the number in the hash map. In the end, when all the 3 digit numbers are generated, print all the numbers which have a frequency of more than 1.

Below is the implementation of the above idea:

C++

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// CPP program to print 3 digit repeating numbers
#include <bits/stdc++.h>
using namespace std;
  
// function to print 3
// digit repeating numbers
void printNum(string s)
{
    int i = 0, j = 0, val = 0;
  
    // Hashmap to store the
    // frequency of a 3 digit number
    map <int, int> mp;
  
    // first three digit number
    val = (s[0] - '0') * 100
            + (s[1] - '0') * 10
            + (s[2] - '0');
  
    mp[val] = 1;
    for (i = 3; i < s.length(); i++) {
        val = (val % 100) * 10 + s[i] - '0';
  
        // if key already exists
        // increase value by 1
        if (mp.find(val) != mp.end()) {
            mp[val] = mp[val] + 1;
        }
        else {
            mp[val] = 1;
        }
    }
  
    // Output the three digit numbers with frequency>1
    for (auto m : mp) {
        int key = m.first;
        int value = m.second;
        if (value > 1)
            cout << key  << " - " << value << " times" << endl;
    }
}
  
// Driver Code
int main() 
{
    // Input string
    string input = "123412345123456";
   
    // Calling Function
    printNum(input);
}
// This code is contributed by Nishant Tanwar

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Java

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// Java program to print 3 digit repeating numbers
import java.util.*;
import java.lang.*;
  
public class GFG {
  
    // function to print 3
    // digit repeating numbers
    static void printNum(String s)
    {
        int i = 0, j = 0, val = 0;
  
        // Hashmap to store the
        // frequency of a 3 digit number
        LinkedHashMap<Integer, Integer> hm
            = new LinkedHashMap<>();
  
        // first three digit number
        val = (s.charAt(0) - '0') * 100
              + (s.charAt(1) - '0') * 10
              + (s.charAt(2) - '0');
  
        hm.put(val, 1);
        for (i = 3; i < s.length(); i++) {
            val = (val % 100) * 10 + s.charAt(i) - '0';
  
            // if key already exists
            // increase value by 1
            if (hm.containsKey(val)) {
                hm.put(val, hm.get(val) + 1);
            }
            else {
                hm.put(val, 1);
            }
        }
  
        // Output the three digit numbers with frequency>1
        for (Map.Entry<Integer, Integer> en : hm.entrySet()) {
            int key = en.getKey();
            int value = en.getValue();
            if (value > 1)
                System.out.println(key + " - " + value + " times");
        }
    }
  
    // Driver Code
    public static void main(String args[])
    {
  
        // Input string
        String input = "123412345123456";
  
        // Calling Function
        printNum(input);
    }
}

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Output:

123 - 3 times
234 - 3 times
345 - 2 times


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Improved By : Nishant Tanwar