基数排序

 1 #include <stdio.h>
 2 
 3 const int pow10[] = {1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000};
 4 
 5 #define get_digit(num, n) ((num) % pow10[(n)] / pow10[(n) - 1])
 6 
 7 int counting_sort(const int *arr, int size, int *target, int n) {
 8     int count[10] = {0};
 9     for (int i = 0; i < size; ++i) {
10         count[get_digit(*(arr + i), n)]++;
11     }
12     if (count[0] == size) {
13         return 0;
14     }
15     for (int i = 1; i < 10; ++i) {
16         count[i] += count[i - 1];
17     }
18     for (int i = size - 1; i >= 0; --i) {
19         *(target + *(count + get_digit(*(arr + i), n)) - 1) = *(arr + i);
20         --*(count + get_digit(*(arr + i), n));
21     }
22     return 1;
23 }
24 
25 void radix_sort(int *arr, int size) {
26     int another[size];
27     int state = 1, i;
28     for (i = 1; state > 0 && i <= 10; ++i) {
29         if (i % 2 > 0) {
30             state = counting_sort(arr, size, another, i);
31         } else {
32             state = counting_sort(another, size, arr, i);
33         }
34     }
35     if (i % 2 > 0 && i <= 10) {
36         for (int j = 0; j < size; ++j) {
37             arr[j] = another[j];
38         }
39     }
40 }
41 
42 int main() {
43     int arr[] = {329, 457, 657, 839, 436, 720, 355};
44     const int size = sizeof(arr) / sizeof(int);
45     radix_sort(arr, size);
46     for (int i = 0; i < size; ++i) {
47         printf("%d\n", arr[i]);
48     }
49     return 0;
50 }

注：基数排序数组元素不能为负，若存在负数可进行偏置处理。

　　如[3, -2, 4]的所有元素偏置+2，变成[5, 0, 6]，基数排序之后再用-2偏置回来。

标签：count,sort,arr,int,state,基数排序,size
来源： https://www.cnblogs.com/zhangshiyu/p/16439135.html