UVa 10469 To Carry or not to Carry (异或)

32位加法器设计错误解析

最新推荐文章于 2025-09-07 21:00:40 发布

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最新推荐文章于 2025-09-07 21:00:40 发布

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分类专栏： UVa acm之路--数学文章标签： UVa acm c++

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本文探讨了一个学生在数字逻辑课程中实现32位加法器时出现的设计错误，即始终忽略进位位导致的计算结果异常。通过一个具体的例子说明了这种错误如何发生，并提供了一个简单的C语言程序来模拟这种错误行为。

10469 - To Carry or not to Carry

Time limit: 3.000 seconds

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=24&page=show_problem&problem=1410

6+9=15 seems okay. But how come 4+6=2?

You see, Mofiz had worked hard throughout his digital logic course, but when he was asked to implement a 32 bit adder for the laboratory exam, he did some mistake in the design part. After tracing the design for half an hour, he found his flaw!! He was doing bitwise addition but his carry bit always had zero output. Thus,

 4 = 00000000 00000000 00000000 00000100
+6 = 00000000 00000000 00000000 00000110
----------------------------------------
 2 = 00000000 00000000 00000000 00000010

Its a good thing that he finally found his mistake, but it was too late. Considering his effort throughout the course, the instructor gave him one more chance. Mofiz has to write an efficient program that would take 2 unsigned 32 bit decimal numbers as input, and produce an unsigned 32 bit decimal number as the output adding in the same was as his circuit does.

Input

In each line of input there will be a pair of integer separated by a single space. Input ends at EOF.

Output

For each line of input, output one line -- the value after adding the two numbers in the "Mofiz way".

Sample Input

4 6
6 9

Sample Output

2
15

0+0=0

0+1=1

1+0=1

1+1=0

这不异或么。。

完整代码：

/*0.015s*/

#include<cstdio>

int main()
{
	int a, b;
	while (~scanf("%d%d", &a, &b))
		printf("%d\n", a ^ b);
	return 0;
}