Question

我正在尝试创建一个C程序，该程序读取标准输入，直到到达输入结束为止，然后将偶数存储到数组中并打印出来。我不知道为什么我的程序无法按预期运行。任何帮助将不胜感激。

#include <stdio.h>
int main(){
    int num = getchar();
    int list[10000];//array to store even nums
    int i = 0;
    while(num != EOF){    
        if(num % 2 == 0){
            list[i] = num;//store even nums
            i++;
        }
        num = getchar();
    }
    for(int j = 0;j < i;j++){
        printf("%d ",list[j]);
    }

    return 0;
}
//example output from terminal

Test 8 (1 1 2 3 5 8 13 21 34) - failed (Incorrect output)
Your program produced these 1 lines of output:
10 10 50 10 10 10 56 10 10 50 10 52 10 
Last line of output above was not terminated with a newline('\n') character

The correct 1 lines of output for this test were:
2 8 34 

The difference between your output(-) and the correct output(+) is:
- 10 10 50 10 10 10 56 10 10 50 10 52 10 
+ 2 8 34 

The input for this test was:
1
1
2
3
5
8
13
21
34

Answer 1

如果仅输入一行，则不必存储所有数字，只需打印它们即可：

#include <stdio.h>

int main(void)
{
    int num;
    while (scanf("%d", &num) == 1) {
        if(num % 2 == 0)
            printf("%d ", num);
    }
    putchar('\n');  // from your output it is clear that
                    // a newline at the end is expected.
    return 0;
}

如果您必须处理多行：

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

int main(void)
{
    size_t capacity = 0;
    int *numbers = NULL;
    size_t count = 0;
    int input;

    while (scanf("%d", &input) == 1) {
        if(input % 2 == 0) {
            if(count == capacity) {
                capacity += 10;
                numbers = realloc(numbers, capacity * sizeof(int));
            }
            numbers[count++] = input;
        }
    }

    for(size_t i = 0; i < count; ++i)
        printf("%d ", numbers[i]);
    putchar('\n');

    free(numbers);
    return 0;
}

Answer 2

getchar()一次只能读取一个char，您需要使用一个读取完整输入的函数。

scanf("%d", &num);

或更好的fgets和strtol：

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

#define N 10000

int main(void)
{
    int list[N];
    int num, i = 0;
    char buf[32], *ptr;

    while ((i < N) && fgets(buf, sizeof buf, stdin)) {
        if (buf[0] == '\n') {
            break;
        }
        num = (int)strtol(buf, &ptr, 10);
        if (*ptr != '\n') { // not a valid number
            continue;
        }
        if (num % 2 == 0) {
            list[i] = num; //store even nums
            i++;
        }
    }
    for (int j = 0; j < i; j++) {
        printf("%d ", list[j]);
    }
    printf("\n");
    return 0;
}

C-存储偶数直到输入结束

2 个答案: