利用基数排序对a[17][4]={" ","COW","DOG","SEA","RUG","ROW","MOB","BOX","TAB","BAR","EAR","TAR","DIG","BIG","TEA","NOW","FOX"}进行排序。
“基数排序”可以看做给“计数排序”创造条件,一般的小数用基数排序很麻烦,而且效率不如计数排序,但是要是n个长度为b的长整数或者字符串,可以先用r(r<=b)进行划分,划分成b/r块,再利用计数排序就很容易了。时间复杂度为O((b/r)(n+2^r)),其中O(n+2^r)是每次计数排序的时间,共进行b/r回计数排序。虽然基数排序比快速排序的平均情况看上去更好,但是它的常数因子却比快速排序大得多,虽然它排序执行的遍数少,但是每一遍花的时间却多得多,而且基数排序不是原地排序,需要额外的内存,这一点不如原地的快速排序节约内存。
#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("待排序数组:\n"); for(i=1;i<=16;i++) { printf("%s ",a[i]); } RadixSort(a,16,3,26); printf("对数组进行基数排序:\n"); for(i=1;i<=16;i++) { printf("%s ",a[i]); } system("pause"); return 0; }