题解 | #单词倒排#

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

void swap(char* a, char* b)
{
    char temp;

    if (a != b) {
        temp = *a;
        *a = *b;
        *b = temp;
    } else {}
}

int main() {
    char s[10001] = {};
    uint32_t length = 0,i;
    uint32_t start,end;

    scanf("%[^\n]*c", s);
    length = strlen(s);
    // 替换非字母字符为空格
    for (i=0; i<length; ++i) {
        if (s[i]<'A' || (s[i]>'Z'&&s[i]<'a') || s[i]>'z') {
            s[i] = ' ';
        } else {}
    }
  
    // 整体反转
    for (start=0,end=length-1; start<end; ++start,--end) {
        swap(&s[start], &s[end]);
    }
  
    // 逐个单词倒排
    for (i=0,start=0,end=0; i<length; ++i) {
        if ((s[i]==' ') || (i==length-1)) {
            if ((i==length-1) && (s[i]!=' ')) {
                end = i;
            } else {
                end = i-1;
            }
            for (; start<end; ++start,--end) {
                swap(&s[start], &s[end]);
            }
            start = i+1;
        } else {}
    }

    printf("%s", s);

    return 0;
}