如何将一个数除3而不使用*、/、+、-、%等运算符?

号码可以有签名,也可以没有签名。


当前回答

使用Linux shell脚本:

#include <stdio.h>
int main()
{
    int number = 30;
    char command[25];
    snprintf(command, 25, "echo $((%d %c 3)) ", number, 47);
    system( command );
    return 0;
}

请看我的另一个答案。

其他回答

这是Python中的,基本上,字符串比较和一个状态机。

def divide_by_3(input):
  to_do = {}
  enque_index = 0
  zero_to_9 = (0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
  leave_over = 0
  for left_over in (0, 1, 2):
    for digit in zero_to_9:
      # left_over, digit => enque, leave_over
      to_do[(left_over, digit)] = (zero_to_9[enque_index], leave_over)
      if leave_over == 0:
        leave_over = 1
      elif leave_over == 1:
        leave_over = 2
      elif leave_over == 2 and enque_index != 9:
        leave_over = 0
        enque_index = (1, 2, 3, 4, 5, 6, 7, 8, 9)[enque_index]
  answer_q = []
  left_over = 0
  digits = list(str(input))
  if digits[0] == "-":
    answer_q.append("-")
  digits = digits[1:]
  for digit in digits:
    enque, left_over = to_do[(left_over, int(digit))]
    if enque or len(answer_q):
      answer_q.append(enque)
  answer = 0
  if len(answer_q):
    answer = int("".join([str(a) for a in answer_q]))
  return answer

这是一个执行所需操作的简单函数。但是它需要+操作符,所以你所要做的就是用位操作符来加值:

// replaces the + operator
int add(int x, int y)
{
    while (x) {
        int t = (x & y) << 1;
        y ^= x;
        x = t;
    }
    return y;
}

int divideby3(int num)
{
    int sum = 0;
    while (num > 3) {
        sum = add(num >> 2, sum);
        num = add(num >> 2, num & 3);
    }
    if (num == 3)
        sum = add(sum, 1);
    return sum; 
}

正如吉姆评论的那样,这是可行的,因为:

N = 4 * a + b N / 3 = a + (a + b) / 3 sum += an = a + b,然后迭代 当a == 0 (n < 4)时,sum += floor(n / 3);即1,如果n == 3,否则为0

log(pow(exp(number),0.33333333333333333333)) /* :-) */

在PHP中使用BC数学:

<?php
    $a = 12345;
    $b = bcdiv($a, 3);   
?>

MySQL(来自Oracle的采访)

> SELECT 12345 DIV 3;

帕斯卡:

a:= 12345;
b:= a div 3;

X86-64汇编语言:

mov  r8, 3
xor  rdx, rdx   
mov  rax, 12345
idiv r8

如果我们认为__div__不是正字法上的/

def divBy3(n):
    return n.__div__(3)

print divBy3(9), 'or', 9//3