首解

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

#define MAX_SIZE 1000

int main() {
    int arr[MAX_SIZE];
    int unique[MAX_SIZE];
    int size = 0;
    int unique_size = 0;
    int num;
    
    while (scanf("%d", &num) == 1) {
        arr[size++] = num;
    }
    
    for (int i = 0; i < size; i++) {
        int is_duplicate = 0;
        for (int j = 0; j < unique_size; j++) {
            if (arr[i] == unique[j]) {
                is_duplicate = 1;
                break;
            }
        }
        if (!is_duplicate) {
            unique[unique_size++] = arr[i];
        }
    }
    
    printf("[");
    if (unique_size > 0) {
        printf("%d", unique[0]);
        for (int i = 1; i < unique_size; i++) {
            printf(", %d", unique[i]);
        }
    }
    printf("]\n");
    
    return 0;
}