我想在 C 中编写一个程序，它将一个数组作为输入并告诉哪个数字是完美的正方形

Question

#include<stdio.h>
#include<math.h>

int perfectSquare(int arr[], int n);
int main()
{
    
    int n , arr[n];
   
    
    printf("number of elements to store in array");
    scanf("%d", &n); 
     for (int i = 0; i < n; i++)
   { 
      printf("enter %d number", i+1);
      scanf("%d", &arr[i]);
   }

    perfectSquare(arr, n);

return 0;
}

int perfectSquare(int arr[], int n)
{
 int i;
 int a;
 for (i = 0; i <= n; i++) //i=4 arr[4]==9   //arr[1]=2 i=1
 {
    a=sqrt((double)arr[i]); //a=3 //a=1.454=1
    if ( a*a==arr[i] )   //a==3*3==9==arr[4]   //a*a=1!=arr[2]
    printf("%d", arr[i]);
 }

}

I am new to coding and I am currently learning c. I came up with this code but it doesn't work can someone tell me what is the problem with this code?

Answer 1

There are a couple of issues with this exercise, but generally you're on the right track. Here, a version of your example with some possible corrections :

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

void perfect_square(int arr[], int n);

int main(void)
{
    int i, n, *arr;
    printf("number of elements to store in array: ");
    scanf("%d", &n);
    if (n <= 0)
        return -1;
    arr = malloc(n*sizeof(int));
    if (arr == NULL)
        return -2;
    for (i = 0; i < n; i++) {
        printf("enter number %d: ", i+1);
        scanf("%d", &arr[i]);
    }
    perfect_square(arr, n);
    free(arr);
    arr = NULL;
    return 0;
}

void perfect_square(int arr[], int n)
{
    int i, a;
    for (i = 0; i < n; i++) {
        a = (int)sqrt((double)arr[i]);
        if (a*a == arr[i])
            printf("%d ", arr[i]);
    }
}

Some hints:

• Arrays, that have an unknown size at compile time are usually allocated with malloc() , and must be deallocated again with free() (see also: alloca() , calloc() , realloc() ). (In "more recent versions of C" there is also the possibility to use variable length arrays , but those can limit the portability of the code).

• Always make sure to check the start value and end condition of for-loops, to prevent out of bound errors.

• And try to consistently format the code, use good names and nice indentation to improve read-, maintain-, reusablilty.