Receive various values and print only the 3 largest ones in c

Question

Hello, I have an activity to be done that consists of receiving values and only stop receiving them when typing -1, then the program should display the 3 highest values typed as if it were a ranking of first, second and third place. I broke my head a lot and managed to write the program, I receive all values, but at the time of printing it always shows -1 in the 3 printing houses(-1 is the command that for the loop to receive the values)I believe it is a very slight mistake that is compromising the program.Thank you for understanding. The activity describes that vectors should not be used.Before asking the name of the variables plu, slu and tlu are to represent first second and third place.

#include <stdio.h>
#include <stdlib.h>

main()
{
  int pon = 0, plu, slu, tlu;

  while (pon != -1)
  {
    printf("Insira a pontuacao dos jogadores\n");
    scanf("%d", &pon);
    plu = pon ;
    slu = pon ;
    tlu = pon ;
  }

  if (plu >= slu)   
    if (slu >= tlu)
      printf(" 1 Lugar %d\n 2 Lugar %d\n 3 Lugar %d\n",plu,slu,tlu);
    else 
      if (plu >= tlu)
        printf(" 1 Lugar %d\n 3 Lugar %d\n 2 Lugar %d\n", plu, tlu, slu);
      else
        printf(" 3 Lugar %d\n 1 Lugar %d\n 2 Lugar %d\n", tlu, plu, slu);
      else
        if (slu >= tlu)
          if (plu >= tlu)
            printf(" 2 Lugar %d\n 1 Lugar %d\n 3 Lugar %d\n", slu, plu, tlu);   
          else
            printf(" 2 Lugar %d\n 3 Lugar %d\n 1 Lugar %d\n", slu, tlu, plu);
        else
          printf(" 3 Lugar %d\n 2 Lugar %d\n 1 Lugar %d\n", tlu, slu, plu);

  return 0; 
}

Answer 1

1. first mistake:

the reason you are always giving -1 is that Voce le option then stores in the variables and only after storing or not in them will be checked if it is -1 or n, then the variables will always be the last number that was typed,

2. second mistake:

while you are assigning the same value to all placements, you have to make checks to see if they are larger or not than the values previously assigned

    #include <stdio.h>
    main() 
    { 
        int pon = 0,
            plu = 0,
            slu = 0,
            tlu = 0;
        while (pon!=-1)
        {
            if(pon >= plu)
            {
                tlu = slu;
                slu = plu;
                plu = pon;
            }
            if(pon >= slu && pon < plu)
            {
                tlu = slu;
                slu = pon;
            }
            if(pon >= tlu && pon < slu)
                tlu = pon;
            printf("Insira a pontuacao dos jogadores\n");
            scanf("%d", &pon);
        }
        printf("%d | %d | %d \n", plu, slu, tlu);
    }

Answer 2

The main error in your program is that in the main loop it appeals reads the input (Pon) and always assigns it to the plu, slu and tlu variables. Therefore, the last read value (-1) will always be stored in the three variables. Comparisons have to be performed within the loop to know what are the three highest values.

The above @tredeneo solution has an error. Once only equal values are entered they will all be assigned to the same player leaving the rest with 0. Ex:

entrada: 1, 1, -1  --> saída: 1, 0, 0 (erro)
entrada: 2, 1, 1, 1, 1, 1, 1, 1, -1 --> saída: 2, 1, 0 (erro)

Below is a version I made of the program.

#include <stdio.h>

int main(int argc, char *argv[])
{
    int entrada, x1, x2, x3;
    x1 = x2 = x3 = 0;

    do {
        printf("Insira a pontuacao dos jogadores\n");
        scanf("%d", &entrada);

        if (entrada == -1) {
            break;
        } else if (entrada > x1) {
            x3 = x2;
            x2 = x1;
            x1 = entrada;
        } else if (entrada > x2 && entrada <= x1) {
            x3 = x2;
            x2 = entrada;
        } else if (entrada > x3 && entrada <= x2) {
            x3 = entrada;
        }
    } while (entrada != -1);

    printf(" 1 Lugar %d\n 2 Lugar %d\n 3 Lugar %d\n", x1, x2, x3);
    return 0;
}

Answer 3

Implementation with scanf testing.

#include <stdio.h>

int main(void)
{
  int n, pon, plu = -1, slu = -1, tlu = -1;

  do
  {
    printf("*\n");
    printf("* pontos (-1 para fim): ");

    n = scanf("%d", &pon);
    scanf("%*[^\n]");

    if (n != 1)
    {
      printf("* entrada de dados invalida!\n");
      pon = 0;
    }

    else if (pon > plu)
    {
      tlu = slu;
      slu = plu;
      plu = pon;
    }

    else if (pon > slu)
    {
      tlu = slu;
      slu = pon;
    }

    else if (pon > tlu)
    {
      tlu = pon;
    }

    printf("* plu=%d slu=%d tlu=%d\n", plu, slu, tlu);
  } while (pon != -1);

  printf("*\n");
}

Testing:

[~/Projects/testes/so]
$./383228
*
* pontos (-1 para fim): 12
* plu=12 slu=-1 tlu=-1
*
* pontos (-1 para fim): 5
* plu=12 slu=5 tlu=-1
*
* pontos (-1 para fim): 7
* plu=12 slu=7 tlu=5
*
* pontos (-1 para fim): v
* entrada de dados invalida!
* plu=12 slu=7 tlu=5
*
* pontos (-1 para fim): 6 7777777777777777777
* plu=12 slu=7 tlu=6
*
* pontos (-1 para fim): -1
* plu=12 slu=7 tlu=6
*

[~/Projects/testes/so]
$

Answer 4

Initialize with an invalid value (I used -1) and at each read check if it is one of the first three, move the smallest and put it in place.

#include <stdio.h>

int main() {
    int pon = 0, plu=-1, slu=-1, tlu=-1;
    printf("Insira a pontuacao dos jogadores [-1 para encerrar]: ");
    scanf("%d", &pon);
    while (pon != -1) {
        if (pon > plu) {
            tlu = slu;
            slu = plu;
            plu = pon;
        }
        else {
            if (pon > slu) {
                tlu = slu;
                slu = pon;
            }
            else {
                if (pon > tlu) {
                    tlu = pon;
                }
            }
        }
        printf("Insira a pontuacao dos jogadores [-1 para encerrar]: ");
        scanf("%d", &pon);
    }
    printf(" 1 Lugar %d\n 2 Lugar %d\n 3 Lugar %d\n", plu, slu, tlu);
    return 0; 
}