Question

这是我编写的一个程序，它应该使用选择排序方法按字母顺序对单个字符的字符进行排序。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char str[100];

void alphaOrder(){

for(int i=0;str[i]!='\0';++i){                                    //iterate until end of entered string
   if(str[i+1]==' ' || str[i+1]==NULL){        // iterate until end of current word    

          int wordLength=0;                                                 // finds amount of letters in current word    
          for(int j=i;j>=0 && str[j]!=' ';j--){                    
            wordLength+=1;
          }
          int smallest=1000;                   
          int prv = 1000;

          for(int k=0;k != wordLength;++k){
                int counter=0;                                     //loops through letters in word printing and storing the smallest
                while(counter!=wordLength){     
                    if(k==0){                                                   // this if loop only occurs during for 1st char of word
                        if(str[i-counter] < smallest){
                        smallest=str[i-counter];
                         }
                    }

                    else{
                        if(str[i-counter] > smallest && str[i-counter] < prv){
                            smallest=str[i-counter];
                            prv=smallest;
                        }
                    }
                 ++counter;
                }   
                printf("%c",smallest);      
            }           
    }
}

但是我的问题源于这个片段中的逻辑：

for(int k=0;k != wordLength;++k){
                int counter=0;                                     //loops through letters in word printing and storing the smallest
                while(counter!=wordLength){     
                    if(k==0){                                                   // this if loop only occurs during for 1st char of word
                        if(str[i-counter] < smallest){
                        smallest=str[i-counter];
                         }
                    }

                    else{
                        if(str[i-counter] > smallest && str[i-counter] < prv){
                            smallest=str[i-counter];
                            prv=smallest;
                        }
                    }
                 ++counter;
                }   
                printf("%c",smallest);

例如：

input: hello world
output:eoooo ddddd

我知道这个问题源于逻辑，但已经过了一周，我仍然无法正确实现选择排序算法或弄清楚我需要什么。所以任何建议或建议都受到欢迎

Answer 1

像这样

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

void alphaOrder(char *str){
    char *p = str;
    while(*p){
        while(isspace((unsigned char)*p))
            ++p;//skip space
        if(!*p)//end of string?
            break;
        char *word = p;//top of word
        while(*p && !isspace((unsigned char)*p))
            ++p;//in word
        //selection sort
        int word_length = p - word;
        for(int i = 0; i < word_length -1; ++i){
            int smallest = i;
            for(int j = i + 1; j < word_length; ++j){
                if(word[smallest] > word[j])
                    smallest = j;
            }
            if(i != smallest){
                char temp = word[i];
                word[i] = word[smallest];
                word[smallest] = temp;
            }
        }
    }
}
int main(void){
    char str[100+1];
    fgets(str, sizeof str, stdin);
    alphaOrder(str);
    puts(str);
}

选择排序Char C.

1 个答案: