利用基數排序對a[17][4]={" ","COW","DOG","SEA","RUG","ROW","MOB","BOX","TAB","BAR","EAR","TAR","DIG","BIG","TEA","NOW","FOX"}進行排序。
“基數排序”可以看做給“計數排序”創造條件,一般的小數用基數排序很麻煩,而且效率不如計數排序,但是要是n個長度爲b的長整數或者字符串,可以先用r(r<=b)進行劃分,劃分成b/r塊,再利用計數排序就很容易了。時間複雜度爲O((b/r)(n+2^r)),其中O(n+2^r)是每次計數排序的時間,共進行b/r回計數排序。雖然基數排序比快速排序的平均情況看上去更好,但是它的常數因子卻比快速排序大得多,雖然它排序執行的遍數少,但是每一遍花的時間卻多得多,而且基數排序不是原地排序,需要額外的內存,這一點不如原地的快速排序節約內存。
#include <string.h>
#include <time.h>
#define BUFFER_SIZE 10
void CountingSort(char (*a)[4],int len,int index,int k)
{
char b[len+1][4];
int c[k];
int i=0;
for(i=0;i<k;i++)
{
c[i]=0;
}
for(i=1;i<=len;i++)
{
c[a[i][index]-'A']++;
}
for(i=1;i<k;i++)
{
c[i]+=c[i-1];
}
for(i=len;i>0;i--)
{
strcpy(b[c[a[i][index]-'A']],a[i]);
c[a[i][index]-'A']--;
}
for(i=1;i<=len;i++)
{
strcpy(a[i],b[i]);
}
}
void RadixSort(char (*a)[4],int len,int d,int k)
{
int i=0;
for(i=d-1;i>=0;i--)
{
CountingSort(a,len,i,k);
}
}
int main()
{
int i=0;
char a[17][4]={" ","COW","DOG","SEA","RUG","ROW","MOB","BOX","TAB","BAR","EAR","TAR","DIG","BIG","TEA","NOW","FOX"};
printf("待排序數組:\n");
for(i=1;i<=16;i++)
{
printf("%s ",a[i]);
}
RadixSort(a,16,3,26);
printf("對數組進行基數排序:\n");
for(i=1;i<=16;i++)
{
printf("%s ",a[i]);
}
system("pause");
return 0;
}