2-8

2-8.c

#include <stdio.h>

int rightrot(unsigned x, int n);
int main(){
  int x = 0b111010;
  printf("%d\n",rightrot(x, 2));
  // 111010 -> 101110 = 46
}

int rightrot(unsigned x, int n){
  int i = 0;
  int nx = x;
  while(nx > 0){
    nx /= 2;
    i++;
  }
//  printf("i:%d\n",i);
  if(i < n){
    printf("桁数が足りません\n");
    return -1;
  }else{
    //下n桁の数字をとる
    int shiftbit = x & ~(~0 << n);
//    printf("sb:%d\n", shiftbit);
    //n桁右シフト
    x = x >> n;
//    printf("shifted_x:%d\n", x);
    //下n桁をnumber - n 左シフト
    shiftbit = shiftbit << (i - n);
    //足す
    return x + shiftbit;
  }
}