无输出 - 程序不提供任何输出

Question

我正在学习数据结构。我尝试编写一个函数 rotate(arr[], d, n) 将大小为 n 的 arr[] 旋转 d 个元素。

我所说的旋转是指移动数组中的元素。

程序没有给出任何错误，而是挂了一点，但没有运行。

代码如下：-

#include <stdio.h>

int rotate(int arr[], int d, int n, int dir)
{
    int temp, i;

    while (d)
    {
        if (dir)
        {

            // for left shift
            // First element will always get replaced in a rotation.
            temp = arr[0];
            for (i = 0; i < n - 1; i++)

                // for left shifting the second element next to its original position.
                arr[i] = arr[i + 1];

            // Putting the temp value in the last position.
            arr[n - 1] = temp;
        }

        else
        {
            // for right shift
            // Last element will always get replaced in a rotation.
            temp = arr[n - 1];
            for (i = n - 1; i > 0; i--)

                // for right shifting the second last element to the last position.
                arr[i] = arr[i - 1];
            // Putting the temp value in the first position
            arr[0] = temp;
        }
        d--;
    }

    // Print the shifted array
    for (i = 0; i < n; i++)
    {
        printf("%d, ", arr[i]);
    }
}

当我不接受用户输入时，程序仅运行s。

int main()
{
    int n;
    int arr[n];
    int dir;
    int d;

    printf("Enter the size of the array: \n");
    scanf("%d", &n);

    printf("Enter the elements of the array: \n");
    for (int i = 1; i <= n; i++)
    {
        printf("Enter element %d", i);
        scanf("%d", &arr[i]);
    }

    printf("Enter the position: \n");
    scanf("%d", &d);

    printf("Enter the direction: \n");
    // 0: Right Direction and 1: Left Direction
    scanf("%d", &dir);


    // Before shifting the array
    for (int i = 1; i <= n; i++)
    {
        printf("%d, ", arr[i]);
    }

    // After shifting the array
    rotate(arr, d, n, dir);


    return 0;
}

Answer 1

您可能想在 scanf("%d", &n); 之后执行 int arr[n]，因为在执行 int arr[n] 时 n 未初始化。 C 中的数组索引也从 0 开始，因此 for (int i = 1; i <= n; i++) 将是 for (int i = 0; i < n; i++).

Answer 2

这不是正确答案，所以不要接受它作为正确答案。这只是出于教育目的的可能实现。

这是一种旋转数组的方法，这样每个元素只移动一次（除了“组”的第一个元素是通过临时变量移动的）。

旋转量指定为整数，正值向右旋转，负值向左旋转。它将这个数量转换为 0 到 n-1 范围内的数字，这是将被复制到元素 0 的元素的索引。然后它将数组分成一个或多个相同的交错组大小使得每个组中的连续元素以圆形方式按旋转量分开，并旋转每个组内的元素。（组数为n与旋转量的最大公约数，每组元素个数为元素总数除以组数。）

#include <limits.h>
#include <stddef.h>

static size_t rotate_modulus(int d, size_t n);
static size_t gcd_size(size_t a, size_t b);

/* Rotate arr[] of length n right by d, or left by -d. */
void rotate(int arr[], int d, size_t n)
{
    size_t md = rotate_modulus(d, n);   /* Get offset in range 0 to n-1. */
    if (md)
    {
        /* Rotation needed. */
        /* Divide into interleaved groups and rotate each group. */
        size_t num_groups = gcd_size(n, md);
        size_t group_size = n / num_groups;
        size_t group;
        for (group = 0; group < num_groups; group++)
        {
            size_t a = group;   /* Index of first element in group. */
            size_t i;
            /* Rotate elements in group. */
            int temp = arr[a];  /* Get first element. */
            for (i = 0; i < group_size - 1; i++)
            {
                /* Get index of next element in group. */
                size_t b = (a + md);
                if (a >= n - md)
                {
                    b -= n;         /* Index wraps around. */
                }
                arr[a] = arr[b];    /* Move an element. */
                a = b;              /* Advance to next index. */
            }
            arr[a] = temp;          /* Move first element to last element. */
        }
    }
}

/*
 * Get modulus for rotation of n elements.
 *
 * d is the amount to rotate right; negative d rotates left by -d.
 *
 * For zero n, the return value is 0.
 *
 * For non-zero n, the return value is n - s, where s is d plus an
 * integer multiple of n such that s is in the range 1 to n, and the
 * return value is in the range 0 to n - 1.
 */
static size_t rotate_modulus(int d, size_t n)
{
    size_t md;
    if (n < 2)
    {
        /* No rotation needed if n < 2. */
        md = 0;
    }
    else if (d >= 0)
    {
        /* Non-negative d will rotate right. */
        md = d % n;
        if (md)
        {
            md = n - md;
        }
    }
    else
    {
        /* Negative d will rotate left. */
        /* -d would overflow if d == INT_MIN && INT_MIN == -INT_MAX - 1. */
        int fix_overflow = (d < -INT_MAX);
        md = -(d + fix_overflow) % n;
        if (fix_overflow)
        {
            if (++md == n)
            {
                md = 0;
            }
        }
    }
    return md;
}

/*
 * If both a and b are non-zero, return the greatest common divisor of a and b.
 * Otherwise, return 0.
 */
static size_t gcd_size(size_t a, size_t b)
{
    if (b == 0)
    {
        a = 0;
    }
    else
    {
        do
        {
            size_t t = b;
            b = a % b;
            a = t;
        }
        while (b);
    }
    return a;
}

无输出 - 程序不提供任何输出

No Output - The program doesn't give any output

c

arrays

function

rotation