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Maximum count of unique index 10 or 01 substrings in given Binary string

Given a binary string str of length N, the task is to count the maximum number of adjacent pairs of form “01” or “10” that can be formed from the given binary string when one character can be considered for only one pair.

Examples:

Input: str = “0101110”
Output: 3
Explanation: The three pairs are “01” at the starting first,
“01” starting at 2nd index (0 based indexing)
and “10” at the end of the string.
Notice 2 pairs can also be formed by using “10” from index 1 and “10” at last.
But that does not give the maximum number of adjacent pairs.

Input: str = “0011”
Output: 1

Input: str  = “11”
Output: 0

Approach: This is a implementation based problem. Follow the steps mentioned here to solve the problem:

• Traverse string from left to right.
• Initialize count of pairs with 0 and consider the previous character as free.
• Run a loop from 1 to size of the string.
• Check if the previous character is opposite to the current character or not and also if it is free or not
• If yes then increment count of pairs and set the character as not free.
• Else continue the traversal in the loop considering the character as free.
• Print the count of pairs.

Below is the implementation of the above approach.

C++

 // C++ code to implement the above approach#include using namespace std; // Count pairs functionvoid check_pairs(string str){    // Initialize pairs with 0    int pairs = 0;     // Previous char is free to pair    bool prev_c = true;     // Traverse string from second position    for (int i = 1; i < str.size(); i++) {        // Check both char are opposite or not        // and also check previous char        // is free or not        if (str[i] != str[i - 1] && prev_c) {             // Once previous char paired            // with other make it false            prev_c = false;             // Increment pairs count            pairs++;        }        else {             // Previous char is free for pair            prev_c = true;        }    }     // Print count of pairs of two characters    cout << pairs;} // Driver Codeint main(){    string str = "0101110";     // Function call    check_pairs(str);    return 0;}

Java

 // Java code to implement the above approachclass GFG{   // Count pairs function  static void check_pairs(String str)  {     // Initialize pairs with 0    int pairs = 0;     // Previous char is free to pair    boolean prev_c = true;     // Traverse String from second position    for (int i = 1; i < str.length(); i++)    {       // Check both char are opposite or not      // and also check previous char      // is free or not      if (str.charAt(i) != str.charAt(i - 1) && prev_c) {         // Once previous char paired        // with other make it false        prev_c = false;         // Increment pairs count        pairs++;      }      else {         // Previous char is free for pair        prev_c = true;      }    }     // Print count of pairs of two characters    System.out.println(pairs);  }   // Driver Code  public static void main(String args[])  {    String str = "0101110";     // Function call    check_pairs(str);  }} // This code is contributed by gfgking

Python3

 # python3 code to implement the above approach # Count pairs functiondef check_pairs(str):     # Initialize pairs with 0    pairs = 0     # Previous char is free to pair    prev_c = True     # Traverse string from second position    for i in range(1, len(str)):               # Check both char are opposite or not        # and also check previous char        # is free or not        if (str[i] != str[i - 1] and prev_c):             # Once previous char paired            # with other make it false            prev_c = False             # Increment pairs count            pairs += 1         else:             # Previous char is free for pair            prev_c = True     # Print count of pairs of two characters    print(pairs) # Driver Codeif __name__ == "__main__":     str = "0101110"     # Function call    check_pairs(str) # This code is contributed by rakeshsahni

C#

 // C# code to implement the above approachusing System;class GFG{   // Count pairs function  static void check_pairs(string str)  {     // Initialize pairs with 0    int pairs = 0;     // Previous char is free to pair    bool prev_c = true;     // Traverse string from second position    for (int i = 1; i < str.Length; i++)    {       // Check both char are opposite or not      // and also check previous char      // is free or not      if (str[i] != str[i - 1] && prev_c) {         // Once previous char paired        // with other make it false        prev_c = false;         // Increment pairs count        pairs++;      }      else {         // Previous char is free for pair        prev_c = true;      }    }     // Print count of pairs of two characters    Console.Write(pairs);  }   // Driver Code  public static int Main()  {    string str = "0101110";     // Function call    check_pairs(str);    return 0;  }} // This code is contributed by Taranpreet

Javascript



Output

3

Time Complexity: O(N)
Auxiliary Space: O(1)

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