End loop if array is empty

Question

To solve my problem I need to get out of the while loop if the str2 is empty.

while (elementos <= tamanho - jogada || str2 == NULL);

This is the code:

#include <stdio.h>
#include <string.h>

#define BUFFER 100

unsigned int randaux() {
    static long seed = 1;
    return (((seed = seed * 214013L + 2531011L) >> 16) & 0x7fff);
}

/* Implementação do procedimento MostraLamberta */

unsigned int MostraLamberta(int *tabuleiro, int tamanho) {
    int i, casa, elementos;
    int jogada = 0;
    char novostr[BUFFER], str2[BUFFER];    /* novo vetor para receber os char */
    do {
        scanf("%d %d", &casa, &elementos);
        for (i = 0; i < tamanho; i++) {    /*Loop para percorrer o int tabuleiro um a um */
            if (tabuleiro[i] == 0) {       /*Comparar se for 0 vai para o vetor como O */
                novostr[i] = 'O';
            } else {            /* Se não vai para o vetor como X */
                novostr[i] = 'X';
            }
        }
        if (tamanho >= 10) {
            novostr[i] = '\0';
            for (i = 1; i < tamanho; i++) {
                if (i == 10) {
                    printf("%d", (i) / 10);
                } else {
                    printf(" ");
                }
            }
            printf("\n");
            for (i = 1; i < tamanho + 1; i++) {
                if (i >= 10) {
                    printf("%d", i % 10);
                } else {
                    printf("%d", i);
                }
                printf;
            }
        } else {
            for (i = 0; i < tamanho; i++) {
                if (i == 10) {
                    printf("%d", i % 10);
                } else {
                    printf("%d", i + 1);
                }
            }
        }
        printf("\n");
        novostr[i] = '\0';    /*Termina a string */
        jogada++;
        printf("%s", novostr);
        printf("\nJogada [%d]: %d %d", jogada, casa, elementos);    /*Imprime nova string */
        for (i = casa - 1; i < elementos + casa - 1; i++) {
            if (tabuleiro[i] == 0) {    /*Comparar se for 0 vai para o vetor como O */
                novostr[i] = 'X';
                tabuleiro[i] = 1;
                continue;
            } else {            /* Se não vai para o vetor como X */
                novostr[i] = 'O';
                tabuleiro[i] = 0;
                str2[i] = tabuleiro[i];
            }
            novostr[i] = '\0';

            printf("%d", str2[i]);//in here if its empty, the loop is over
        }
        printf("\n");

    } while (elementos <= tamanho - jogada || str2 == NULL);

    if (jogada % 2 == 0) {
        printf("Jogada inválida, perde jogador 2.");
    } else {
        printf("Jogada inválida, perde jogador 1.");
    }
}

void main() {
    int i, num, saltos, tamanho, tabuleiro[BUFFER];    /*Implementa as variáveis inteiras */
    scanf("%d %d", &tamanho, &saltos);

    // saltar os primeiros números aleatórios, para ter sequências distintas
    for (i = 0; i < saltos; i++)    /*Loop */
        randaux();            /*Chama a funcão randaux */

    /* Chamar o procedimento para gerar um novo tabuleiro */
    for (i = 0; i < tamanho; i++) {
        num = randaux();        /*Grava um numero aleatório numa nova variável */
        if (num % 2 == 0) {     /*VC* se o numero aleatório C) par ou impar */
            tabuleiro[i] = 0;
        } else {
            tabuleiro[i] = 1;
        }
    }

    MostraLamberta(tabuleiro, tamanho);    /*Chama a função e passa dois argumentos) */
}

[ my output ]

[ expected output ]

Hi, sorry for my english. Like the output the loops dont break if the str2 array its empty. printf("%d", str2[i]);//in here if its empty, the loop is over — Ricardo Costa
– Ricardo Costa, Commented Nov 20, 2022 at 15:21

chqrlie · Accepted Answer · 2022-11-20 17:47:49Z

1

It is unclear what your code does, but there are some problems:

the do / while loop is an error prone construction. It is less confusing to use a for (;;) (aka for ever) loop and make explicit tests to break from it, such as if (scanf("%d %d", &casa, &elementos) != 2) break;
the second part of the test while (elementos <= tamanho - jogada || str2 == NULL); is moot: str2 is an array, it cannot be NULL. If you want to test for an empty string, use str2[0] == '\0' instead.
str2 is not properly constructed: the only place where it gets modified is: str2[i] = tabuleiro[i]; but tabuleiro[i] is set to 0 just before this statement, so part of str2 is uninitialized and the only elements that get modified are null bytes.

answered Nov 20, 2022 at 17:47

chqrlie

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dash-o · Accepted Answer · 2022-11-20 17:19:54Z

0

In the OP code, the following lines get into infinite loop.

while (elementos <= tamanho - jogada || str2 == NULL);

Few potential issues to look at:

The 'str2' expression is always NON-null. Recall that in "C", the value of an array is the address of the first element. If you want to test is a string is "empty" consider strlen(str2) == 0, or similar.
For any case that str2 is "not empty", the while will go into infinite loop if elementos <= tamanho - jogada. Usually, you will see modification to one of the variables in the condition inside the loop body. e.g. jopada++

answered Nov 20, 2022 at 17:19

dash-o

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