c - 需要帮助了解此C代码(数组)

我需要帮助以清楚地了解此代码，请提供帮助。我无法弄清楚这个程序如何跟踪响应数组中给出了多少个数字。
我不明白for循环的情况，特别是这行++ frequency [responses [answer]];

    #include<stdio.h>
    #define RESPONSE_SIZE 40
    #define FREQUENCY_SIZE 11

    int main(void)
    {
        int answer; /* counter to loop through 40 responses */
        int rating; /* counter to loop through frequencies 1-10 */

        /* initialize frequency counters to 0 */

        int frequency[FREQUENCY_SIZE] = {0};

        /* place the survey responses in the responses array */

        int responses[RESPONSE_SIZE] = {1,2,6,4,8,5,9,7,8,10,1,6,3,8,6,10,3,8,2,7,6,5,7,6,8,6,7,5,6,6,5,6,7,5,6,4,8,6,8,10};

        /* for each answer, select value of an element of array responses
        and use that value as subscript in array frequency to determine element to increment */

        for(answer = 0 ; answer < RESPONSE_SIZE; answer++){
            ++frequency[responses[answer]];
        }

        printf("%s%17s\n", "Rating", "Frequency");

        /* output the frequencies in a tabular format */
        for(rating = 1; rating < FREQUENCY_SIZE; rating++){
            printf("%6d%17d\n", rating, frequency[rating]);
        }

        return 0;
    }

最佳答案

++frequency[responses[answer]]是一种密集的书写方式

int r = response[answer];
frequency[r] = frequency[r] + 1;

请注意，frequency[r]仅计算一次。

因此，如果answer等于0，则responses[answer]等于1，因此我们将1添加到frequency[1]。

编辑

下表显示了frequency在循环中发生的情况（旧值=>新值）：

answer    response[answer]    frequency[response[answer]]
------    ----------------    ---------------------------
     0                   1           frequency[1]: 0 => 1
     1                   2           frequency[2]: 0 => 1
     2                   6           frequency[6]: 0 => 1
     3                   4           frequency[4]: 0 => 1
   ...                 ...           ...
    10                   1           frequency[1]: 1 => 2

等等

关于c - 需要帮助了解此C代码(数组)，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/39428649/