C 解法, 执行用时: 1ms, 内存消耗: 256KB, 提交时间: 2020-07-07

#include "stdio.h"

int main()
{
    char s[10000] = {0};
    char chr = 0;
    int len = 0;
    int flag = 0;
    int  end=0,start=0;
    int first = 0;
    while (1)
    {
        scanf("%c", &chr);
        if (chr == '\n')
            break;
        
        s[len++] = chr;
    }
    
    for (int i=len;i>0;i--)
    {
        if ((s[i-1] >= 'a' && s[i-1] <= 'z') || (s[i-1] >= 'A' && s[i-1] <= 'Z')) // 
        {
            if (flag == 0)
            {
                flag = 1;
                end = i;
            }
        }
        else
        {
            if (flag == 1)
            {
                flag = 0;
                start = i;
                
                if (first == 0)
                    first = 1;
                else
                    printf(" ");
                
                for (int j=start;j<end;j++)
                    printf("%c",s[j]);

                start = 0;
                end = 0;
            }
        }
        if (i==1 )
        {
            if (end != 0)
            {
                printf(" ");
                for (int j=start;j<end;j++)
                    printf("%c",s[j]);
            }
            printf("\n");
        }
    }
}

C 解法, 执行用时: 1ms, 内存消耗: 276KB, 提交时间: 2020-12-26

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

int main(void){
    const int col = 100;
    char w[col][50];
    char *words[col];
    int i, top;
    int ind = 0;
    for(top = 0; scanf("%s", w + top) == 1; ++top){
        char *p = w[top];
        while(*p && !isalpha(*p)) ++p;
        if(!*p) continue;
        words[ind++] = p;
        for(; *p; ++p){
            if(!isalpha(*p)){
                *p = '\0';
                if(isalpha(*(p + 1))) words[ind++] = p+1;
            }
        }
    }
    for(i = ind - 1; i > 0; --i) printf("%s ", words[i]);
    puts(words[i]);
    return 0;
}