Question

How to find whether an array include a pair of which product equals to N in C

Answer 1

#include <stdio.h>

int ProductExists(int arr[], int size, int N) {
    for (int i = 0; i < size - 1; i++) {
        for (int j = i + 1; j < size; j++) {
            if (arr[i] * arr[j] == N) {
                return 1; 
            }
        }
    }

    return 0; 
}

int main() {
    int arr[] = { 5, 7, 13, 25, 9, 3, 4 };
    int N = 21;

    int size = sizeof(arr) / sizeof(arr[0]);

    ProductExists(arr, size, N) ? puts("Yes") : printf("No");

    return 0;
}




/*
run:

Yes

*/

 

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Answer 2

#include <stdio.h>

int ProductExists(int arr[], int size, int N) {
    if (size < 2) {
        return 0;
    }

    int result = 0;

    for (int i = 0; i < size - 1; i++) {
        if (arr[i] == 0 && N == 0) {
            return 1;
        }

        if (N % arr[i] == 0) {
            if (result == N / arr[i]) {
                return 1;
            }
            result = arr[i];
        }
    }

    return 0; 
}

int main() {
    int arr[] = { 5, 7, 13, 25, 9, 3, 4 };
    int N = 21;

    int size = sizeof(arr) / sizeof(arr[0]);

    ProductExists(arr, size, N) ? puts("Yes") : printf("No");

    return 0;
}




/*
run:

Yes

*/

 

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