如何通過放入 scanf 的數字數量來定義數組的限制？

SajLencV02

例如：輸入：420 50 -4 輸出：數字 3 正 2 負 1

同樣的代碼：輸入：420 50 -4 7 輸出：數字 4 正 3 負 1在此處輸入圖像描述

   #include<stdio.h>
 #define N 2 
int main()
{

 int a[N], i=0, n=0, k=0, z=0; 

for(i=0; i<N; i++)
 {

 scanf("%d" , &a[i]);

    if((a[i] >= -10000 && a[i] <= 10000 ))
    n++;
    if(a[i]>0)
    k++;
    if(a[i]<0)
    z++;
 }

 printf("Numbers:%d \n", n);
 printf("Positive:%d \n", k);
 printf("Negative:%d \n", z);

return 0;
}

矢野

此示例允許用戶“無限期”輸入數字，而無需提示輸入多少。當然，你的電腦只有這麼多內存，所以有一個限制，但沒有實際限制。本質上，您需要選擇一個初始大小，然後在達到該大小時動態分配更多空間。

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

#define INITIAL_SIZE 10

void printArray(const int* myArray, size_t numsEntered)
{
    for (size_t i=0; i<numsEntered; i++)
    {
        printf("myArray[%zu] = %d\n", i, myArray[i]);
    }
}

int main(void)
{
    size_t arraySize = INITIAL_SIZE;
    size_t numsEnteredSoFar = 0;
    int* myArray = malloc(sizeof(*myArray) * arraySize);  // initially make room for 10
    if (myArray == NULL) exit(-1);  // whoops, malloc failed, handle this error how you want

    while(1)
    {
        int curEntry;
        printf("enter a number, or 'q' to quit: ");
        if (scanf("%d", &curEntry) == 1)
        {
            // store in the array, increment number of entries
            myArray[numsEnteredSoFar++] = curEntry;

            // here you can check for positives and negatives, or
            // wait to do that at the end. The point of this example
            // is to show how to dynamically increase memory allocation
            // during runtime.

            if (numsEnteredSoFar == arraySize)
            {
                puts("Array limit reached, reallocing");
                // we've reached our limit, need to allocate more memory to continue.
                // The expansion strategy is up to you, I'll just continue to add
                // INITIAL_SIZE
                arraySize += INITIAL_SIZE;
                int* temp = realloc(myArray, arraySize * sizeof(*myArray));
                if (temp == NULL)
                {
                    // uh oh, out of memory, handle this error as you want. I'll just
                    // print an error and bomb out
                    fprintf(stderr, "out of memory\n");
                    exit(-1);
                }
                else
                {
                    // realloc succeeded, we can now safely assign temp to our main array
                    myArray = temp;
                }
            }
        }
        else
        {
            // the user entered 'q' (or anything else that didn't match an int), we're done
            break;
        }
    }

    // print the array just to show it worked. Instead, here you can
    // loop through and do your comparisons for positive and negative,
    // or you can continue to track that after each entry as you've
    // shown in your code
    printArray(myArray, numsEnteredSoFar);

    free(myArray);
    return 0;
}