第十五周项目项目4

设计一个基数排序的算法，将一组英文单词，按字典顺序排列。假设单词均由小写字母或空格构成，最长的单词有MaxLen个字母。

[参考解答]

#include <stdio.h>#include <malloc.h>#include <string.h>#define MaxLen 9                //单词的最大长度#define Radix  27               //基数rd为27,分别对应' ','a',…'z'typedef char String[MaxLen+1];  //定义String为字符数组类型typedef struct node{    String word;    struct node *next;} LinkNode;void DispWord(String R[],int n) //输出单词{    int i;    printf("  ");    for (i=0; i<n; i++)        printf("[%s] ",R[i]);    printf("\n");}void PreProcess(String R[],int n)//对单词进行预处理,用空格填充尾部至MaxLen长{    int i,j;    for (i=0; i<n; i++)    {        if (strlen(R[i])<MaxLen)        {            for (j=strlen(R[i]); j<MaxLen; j++)                R[i][j]=' ';            R[i][j]='\0';        }    }}void EndProcess(String R[],int n)//恢复处理,删除预处理时填充的尾部空格{    int i,j;    for (i=0; i<n; i++)    {        for (j=MaxLen-1; R[i][j]==' '; j--);        R[i][j+1]='\0';    }}void Distribute(String R[],LinkNode *head[],LinkNode *tail[],int j,int n)//按关键字的第j个分量进行分配,进入此过程时各队列一定为空{    int i,k;    LinkNode *p;    for (i=0; i<n; i++)         //依次扫描R[i],将其入队    {        if (R[i][j]==' ')       //空格时放入0号队列中,'a'时放入1号队列中,…            k=0;        else            k=R[i][j]-'a'+1;        p=(LinkNode *)malloc(sizeof(LinkNode)); //创建新结点        strcpy(p->word,R[i]);        p->next=NULL;        if (head[k]==NULL)        {            head[k]=p;            tail[k]=p;        }        else        {            tail[k]->next=p;            tail[k]=p;        }    }}void Collect(String R[],LinkNode *head[])//依次将各非空队列中的记录收集起来{    int k=0,i;    LinkNode *p;    for (i=0; i<Radix; i++)        for (p=head[i]; p!=NULL; p=p->next)            strcpy(R[k++],p->word);}void RadixSort(String R[],int n)    //对R[0..n-1]进行基数排序{    LinkNode *head[Radix],*tail[Radix]; //定义Radix个队列    int i,j;    for (i=MaxLen-1; i>=0; i--)             //从低位到高位做d趟箱排序    {        for (j=0; j<Radix; j++)            head[j]=tail[j]=NULL;           //队列置空        Distribute(R,head,tail,i,n);        //第i趟分配        Collect(R,head);                    //第i趟收集    }}int main(){    int n=6;    String R[]= {"while","if","if else","do while","for","case"};    printf("排序前:\n");    DispWord(R,n);    PreProcess(R,n);    printf("预处理后:\n");    DispWord(R,n);    RadixSort(R,n);    printf("排序结果:\n");    DispWord(R,n);    EndProcess(R,n);    printf("最终结果:\n");    DispWord(R,n);    printf("\n");    return 0;}