排序算法3---计数排序 2011-03-23 15:27 125人阅读 评论(0) 收藏

1.算法思想：

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算法的步骤如下：

1. 找出待排序的数组中最大和最小的元素
2. 统计数组中每个值为 i 的元素出现的次数，存入数组 C 的第 i 项
3. 对所有的计数累加（从 C 中的第一个元素开始，每一项和前一项相加）
4. 反向填充目标数组：将每个元素 i 放在新数组的第 C(i) 项，每放一个元素就将 C(i) 减去 1

伪代码：

COUNTING-SORT(A, B, k) 1 for i ← 0 to k 2 do C[i] ← 0 3 for j ← 1 to length[A] 4 do C[A[j]] ← C[A[j]] + 1 5 ▹ C[i] now contains the number of elements equal to i. 6 for i ← 1 to k 7 do C[i] ← C[i] + C[i - 1] 8 ▹ C[i] now contains the number of elements less than or equal to i. 9 for j ← length[A] downto 1 10 do B[C[A[j]]] ← A[j] 11 C[A[j]] ← C[A[j]] - 1

源代码：

#include <stdlib.h> void counting_sort(SORT_TYPE array[], SORT_TYPE size) { SORT_TYPE i, min, max; min = max = array[0]; for(i = 1; i < size; i++) { if (array[i] < min) min = array[i]; else if (array[i] > max) max = array[i]; } SORT_TYPE range = max - min + 1; SORT_TYPE *count = (SORT_TYPE*)malloc(range * sizeof(SORT_TYPE)); for(i = 0; i < range; i++) count[i] = 0; for(i = 0; i < size; i++) count[ array[i] - min ]++; int j, z = 0; for(i = min; i <= max; i++) for(j = 0; j < count[ i - min ]; j++) array[z++] = i; free(count); }

 

注：以上代码来源于维基百科。

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