C language interview exercise questions, please write functions, exercise questions Function

C language interview exercise questions, please write functions, exercise questions Function

Question: Compile the Function

Unsigned int reverse_bits (unsigned int value );

The return value of this function is the value after the binary bitwise mode of value is changed from left to right. For example, on a 32-bit machine, the value 25 contains the following bits:

0000 0000 0000 0000 0000 0000 0001

The Return Value of the function should be 2550 136 832, and its binary bit is:

1001 1000 0000 0000 0000 0000 0000

There are two solutions below, both of which use the shift operation, but the second is more incisive.

The Code is as follows:

# Include
 
  
# Include
  
   
# Include
   
    
# Include
    
     
Unsigned int reverse_bit (unsigned int value) {unsigned int sum = 0; int I = 0; int bit = 0; for (I = 0; I <= 31; I ++) {bit = value & 1; sum + = bit * pow (2, (31-i); // pow (I, j) indicates I ^ j; value = value> 1;} return sum;} unsigned int reverse_bits (unsigned int value) {unsigned int answer; unsigned int I; answer = 0; /*** continue as long as I is not 0, which makes the loop irrelevant to the machine font length, thus avoiding the portability problem */for (I = 1; I! = 0; I <= 1) // control cycle count {answer <= 1; // shift answer left if (value & 1) {answer | = 1 ;} value >>=1; // value shifts to the right, one bit and one bit for comparison} return answer;} int main () {printf ("% u \ n ", reverse_bit (25); // call printf ("% u \ n", reverse_bits (25) for reverse_bits; // call return 0 for reverse_bits ;}