错误导致代码执行

Question

I am trying to create a program in c code, as part of a high school education project, and i have some trouble with my printing results. The main idea is a program which is looking for consequtive non square free numbers teams.The amount of that numbers depends on the value of the preprocessor defined parameter K. For example, if the defined parameter K is set to the value 2, the program should print, after check 2 consecutive non square free numbers. There is no upper number limit for checking. However, the code i wrote works successfully only for the parameter one. Is ther any correction i shoyld do in order to working properly? There is the part of the code i have made:

#include <stdio.h>
#include <stdlib.h>
/* Including the math library for sqrt function */
#include <math.h>
/* Testing Environment values */
#define K 2

int main (void) {
    // Declaration and appropriate Initialization of Variables Section
    unsigned int num = 0, last = 0, count = 0, i, j, lim, Div, temp, start, first, flag;
    long long int div;

    // Non-Squarefree number check section
    for (i = 1; count < K; i++) {
        flag = 0 ;

        for (j = 2; (j <= sqrt(i)) && (count < K); j++) {
            while (( (i % (j * j)) == 0) && (count < K) ) {
                flag = 1;

                if (count = 0) {
                    num = i; /* Storage of the first checked number in case of success finding the K requested numbers */
                }

                count++;
                printf("count++: %d \n", count);
                Div = j;
                last = i;   /* Storage of the last checked number that mets the requested critiria */
                printf("last: %d \n", last);
                break;
            }

            if (flag = 0) { /* Reinitialization of variable values in case of squarefree number */
                count = 0;
                printf("count_null: %d \n", count);
                num = 0;
                printf("count: %d \n", count);
                break;
            }

            break;
        }
    }

    /* test execution prints */
    printf("----------------------------------------") ;
    printf("K: %d \n", K) ;
    printf("last: %d \n", last) ;
    printf("num: %d \n", num);
    start = num;
    return 1;
}

Answer 1

Have a look at these pieces, most notably your if statements.

if (count = 0) {

    // Storage of the first checked number in case
    // of success finding the K requested numbers

    num = i;
}

if (flag = 0) {

    // Reinitialization of variable values in case
    // of squarefree number

    count = 0;
    printf("count_null: %d \n", count);
    num = 0;
    printf("count: %d \n", count);
    break;
}

It's a common issue when getting started with C programming, and it's likely the reason why your code doesn't work. The comparison operator is == , not = because it's already used as the assignment operator.

This means if (count = 0) doesn't run if count equals 0. First it will execute what you put in the statement, which is "set count to 0", or count = 0 . Then if that operation returns 1 (true), the contents of your if statement will execute. On my system (Linux, GCC) count = 0 always returns 0, but I didn't check if it's defined as standard behavior. This mean num = i will never execute, and just passing through that if it will always set count to 0. Which is likely not what you want. Same for if (flag = 0) .

I don't know what the code is supposed to do, maybe that's exactly what you wanted to do. But even if you did, you should never set your variables in an if statement. It's confusing to read and slows you down, and leads to errors. If you really wanted to do what the code you posted does, it would go something like this:

count = 0;

if (0) { // 0 = false
    num = i;
}

This is what your code does. But I'm 99% sure you didn't want that, so start with changing your if s to use == . Let me know if that fixes the issue, and if there's anything more that doesn't work, we'll work it out. Hope that helps!