这意味着您根据数字的第 n 位对数字进行排序。
在您的示例中，您会看到粗体数字（每个数字中的第二个数字）是定义输出顺序的数字。
这是一个解决方法的示例（我现在正在调整它，因为它用于查找数字的方法是错误的）：
#include <stdio.h>
#include <math.h>
void quickSort(int a[], int first, int last, int n_th);
int pivot(int a[], int first, int last, int n_th);
void swap(int* a, int* b);
int n_th_digit(int number, int n);
void print(int array[], const int N);
int main() {
int test[] = { 7, 9, 1, 3, 6, 5, 2, 4 };
int N = sizeof(test) / sizeof(int);
int n_th = 0; // digit(from the end) to sort by
printf("Size of test array : %d\n", N);
printf("Before sorting : \n");
print(test, N);
quickSort(test, 0, N - 1, n_th);
printf("After sorting : \n");
print(test, N);
return 0;
}
/**
* Quicksort.
* @param a The array to be sorted.
* @param first The start of the sequence to be sorted.
* @param last The end of the sequence to be sorted.
* @param n_th The digit to sort by
*/
void quickSort(int a[], int first, int last, int n_th) {
int pivotElement;
if (first < last) {
pivotElement = pivot(a, first, last, n_th);
quickSort(a, first, pivotElement - 1, n_th);
quickSort(a, pivotElement + 1, last, n_th);
}
}
/**
* Find and return the index of pivot element.
* @param a The array.
* @param first The start of the sequence.
* @param last The end of the sequence.
* @param n_th The digit to sort by
* For example the third digit of 137
* requires n_th to be 0.
*
*/
int pivot(int a[], int first, int last, int n_th) {
int i, p = first;
int pivotElement = a[first];
for (i = first + 1; i <= last; i++) {
if (n_th_digit(a[i], n_th) <= n_th_digit(pivotElement, n_th)) {
p++;
swap(&a[i], &a[p]);
}
}
swap(&a[p], &a[first]);
return p;
}
/**
* Swap the parameters.
* @param a The first parameter.
* @param a The second parameter.
*/
void swap(int* a, int* b) {
// You still can use the swap that
// does not uses an extra variable
// from the C++ implementation.
int temp = *a;
*a = *b;
*b = temp;
}
int n_th_digit(int number, int n) {
if (number < 0)
number *= -1;
return fmod((number / pow(10, n)), 10);
}
/**
* Print an array.
* @param a The array.
* @param N The size of the array.
*/
void print(int a[], const int N) {
int i;
for (i = 0; i < N; i++)
printf("array[%d] = %d\n", i, a[i]);
}
我知道了如何从here 中找到第 n 位数字以及从 here 中找到快速排序。