_Find_first() function in C++ bitset with Examples

The _Find_first() is a built-in function in C++ Biteset class which returns an integer that refers the position of first set bit in bitset. If there isn’t any set bit, _Find_first() will return the size of the bitset.

Syntax:

iterator bitset._Find_first()
           or
int bitset._Find_first()

Parameters: The function accepts no parameter.

Return Value: The function returns an integer which refers to the position of first set bit in bitset. If there isn’t any set bit, _Find_first() will return the size of the bitset.

Below is the illustration of the above function:

// C++ program for illustration 
// of _Find_first() function 
  
#include <bits/stdc++.h> 
using namespace std; 
  
#define M 32 
  
int main() 
{ 
    // default constructor initializes with all bits 0 
    bitset<M> bset; 
    bitset<M> bset1; 
  
    // 00000000000000000000000000100000 
    bset[5] = 1; 
  
    // 00000000000000000000010000100000 
    bset[10] = 1; 
  
    // function returns the first set bit in Bitset 
    cout << "position of first set bit in bset\n"; 
    cout << bset._Find_first() << "\n"; 
  
    // function returns bset1.size() 
    // when no bit is set in bitset. 
    cout << "position of first set bit in bset1\n"; 
    cout << bset1._Find_first() << "\n"; 
  
    return 0; 
} 

Output:

position of first set bit in bset
5
position of first set bit in bset1
32

Reference: https://gcc.gnu.org/onlinedocs/libstdc++/libstdc++-html-USERS-3.4/bitset-source.html

GeeksforGeeks has prepared a complete interview preparation course with premium videos, theory, practice problems, TA support and many more features. Please refer Placement 100 for details

My Personal Notes

Recommended Posts: