Find i'th Index character in a binary string obtained after n iterations (original) (raw)

Last Updated : 08 Dec, 2023

Given a decimal number m, convert it into a binary string and apply n iterations. In each iteration, 0 becomes "01" and 1 becomes "10". Find the (based on indexing) index character in the string after the nth iteration.

**Examples:

**Input : m = 5, n = 2, i = 3
**Output : 1
**Input : m = 3, n = 3, i = 6
**Output : 1

Recommended: Please solve it on "_PRACTICE" first, before moving on to the solution.

1. Change a decimal number into a binary and store it in string s.
2. Run loop n times in each iteration. Run another loop of string length s to convert 0 to "01" and 1 to "10" and store in another string s1. After completion of each iteration, assign string s1 to s.
3. Finally, return the value of the ith index in string s.

**Implementation:

C++ `

// C++ Program to find ith character in // a binary string. #include <bits/stdc++.h> using namespace std;

// Function to store binary Representation void binary_conversion(string &s, int m) { while (m) { int tmp = m % 2; s += tmp + '0'; m = m / 2; } reverse(s.begin(), s.end()); }

// Function to find ith character int find_character(int n, int m, int i) {

string s;

// Function to change decimal to binary binary_conversion(s, m);

string s1 = ""; for (int x = 0; x < n; x++) { for (int y = 0; y < s.length(); y++) { if (s[y] == '1') s1 += "10"; else s1 += "01";
}

// Assign s1 string in s string
s = s1;
s1 = "";

} return s[i] - '0'; }

// Driver Function int main() { int m = 5, n = 2, i = 8; cout << find_character(n, m, i); return 0; }

Java

// Java Program to find ith // character in a binary String. import java.io.*; import java.util.Arrays;

class GFG { static String s = ""; static String ReverseString(String s) { char[] arr = s.toCharArray(); for(int i = 0; i < arr.length / 2; i++) { char temp = arr[i]; arr[i] = arr[arr.length - i -1]; arr[arr.length - i - 1] = temp; } return new String(arr); }

// Function to store // binary Representation static void binary_conversion(int m) { while (m != 0) { int tmp = m % 2; s += Integer.toString(tmp); m = (int)(m / 2); }

s = ReverseString(s);

}

// Function to find // ith character static int find_character(int n, int m, int i) {
// Function to change // decimal to binary binary_conversion(m);

String s1 = "";
for (int x = 0; x < n; x++) 
{
    for (int y = 0; 
             y < s.length(); y++) 
    {
        if (s.charAt(y) == '1') 
        s1 += "10";
        else
        s1 += "01";     
    }
    
    // Assign s1 String 
    // in s String
    s = s1;
    s1 = "";
}

return s.charAt(i) - '0';

}

// Driver Code public static void main(String args[]) { int m = 5, n = 2, i = 8; System.out.print( find_character(n, m, i)); } }

// This code is contributed by // Manish Shaw(manishshaw1)

Python3

Python3 Program to find ith character in

a binary string.

Function to store binary Representation

def binary_conversion(s, m): while(m): temp = m % 2 s += str(temp) m = m // 2

return s[::-1]

Function to find ith character

def find_character(n, m, i): s = ""

Function to change decimal to binary

s = binary_conversion(s, m)
s1 = ""

for x in range(n):
    for j in range(len(s)):
        if s[j] == "1":
            s1 += "10"
        else:
            s1 += "01"

# Assign s1 string in s string     
    s = s1
    s1 = ""
e = ord(s[i])
r = ord('0')

return e-r

Driver code

m, n, i = 5, 2, 8

print(find_character(n,m,i))

This code is contributed by mohit kumar 29

C#

// C# Program to find ith // character in a binary string. using System;

class GFG { static string ReverseString(string s) { char[] arr = s.ToCharArray(); Array.Reverse(arr); return new string(arr); }

// Function to store
// binary Representation
static void binary_conversion(ref string s, 
                              int m) 
{
    while (m != 0) 
    {
        int tmp = m % 2;
        s += tmp.ToString();
        m = (int)(m / 2);
    }
    
    s = ReverseString(s);
}

// Function to find 
// ith character
static int find_character(int n, 
                          int m, int i) 
{     
    string s = "";

    // Function to change
    // decimal to binary
    binary_conversion(ref s, m);

    string s1 = "";
    for (int x = 0; x < n; x++) 
    {
        for (int y = 0; y < s.Length; y++) 
        {
            if (s[y] == '1') 
            s1 += "10";
            else
            s1 += "01";     
        }
        
        // Assign s1 string 
        // in s string
        s = s1;
        s1 = "";
    }
    
    return s[i] - '0';
}

// Driver Code
static void Main()
{
    int m = 5, n = 2, i = 8;
    Console.Write(find_character(n, m, i));
}

}

// This code is contributed by // Manish Shaw(manishshaw1)

JavaScript

PHP

`

**Time complexity ****: O(|S|*2^n)**
**Auxiliary Space : O(n)

Refer Set-2 for an optimized solution.

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