Who is the murderer and the ranking of the competition (c language)

scene:

        A homicide occurred in a certain place. The police identified four suspects through investigation, and one of them must be the murderer.

A said: not me

B said: yes C

C said: Yes D

D said: C is talking nonsense

        It is known that one person tells a lie and three tell the truth? Who is the murderer?

analyze:

        When we reason about this question, we will assume that A, B, C, and D are the murderers one by one, and then judge that they meet the condition of "one person lies, three truths".

	Assumption A	Assumption B	Assumption C	Assumption D
A	×	√	√	√
B	×	×	√	×
C	×	×	×	√
D	√	√	√	×

According to the analysis of the table above, it can be seen that C is the murderer.

Code:

int main()
{
    char killer = 0;
    for (killer = 'A'; killer <= 'D'; killer++)
    {
        if ((killer != 'A') + (killer == 'C') + (killer == 'D') + (killer != 'D') == 3)
        {
            printf("%c\n", killer);
        }
    }
    return 0;
}

 Summarize:

        Consider the above checkmark and wrong sign as 1 and 0. So directly judge the three checkmarks, 1+1+1+0 = 3. The simulation result is the same as the reasoning result.

 

---

scene:

        Five athletes participate in the 10-meter platform diving competition, and their predictions are as follows:

A said: B second, I third

B said: I am second, E is fourth

C said: I am first, D is second

D said: C last, I am third

E said: I am fourth, A is first

        It is known that each player is only half right, and programming determines the ranking of the game.

analyze:

        According to the example of the murderer above, it can be analyzed that each person said two conditions. There is one right and one wrong, that is, one 0 and one 1. The ranking of each player may be 1-5, so list all the rankings and judge whether they meet the half of the requirements.

Code:

#include <stdio.h>
int main()
{
	int a = 0;
	int b = 0;
	int c = 0;
	int d = 0;
	int e = 0;

	for (a = 1; a <= 5; a++)
	{
		for (b = 1; b <= 5; b++)
		{
			for (c = 1; c <= 5; c++)
			{
				for (d = 1; d <= 5; d++)
				{
					for (e = 1; e <= 5; e++)
					{
						if (((b == 2) + (a == 3) == 1) && (((b == 2) + (e == 4)) == 1)
							&& (((c == 1) + (d == 2)) == 1) && (((c == 5) + (d == 3)) == 1)
							&& (((e == 4) + (a == 1)) == 1))
						{
							if(a*b*c*d*e == 120)
								printf("a = %d;b = %d;c = %d;d =%d;e = %d\n", a, b, c, d, e);
						}
					}
				}
			}
		}
	}
	return 0;
}

 Summarize:

        List all possible ordering situations, and then make it satisfy the final condition. The reason why the above is equal to 120 is that 1*2*3*4*5 = 120, to prevent two people from ranking in the same place.