反转单词

reverse_sentence.c

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

#define true  1
#define false 0
typedef int bool;

void reverse_sentence(char str[]);
void reverse_string(char str[], int start, int end);

bool reserse_sentence_1(char str[]);

int main(int argc, char* argv[])
{
	char str[] = "abc def ghi jkl   ";
	printf("before --> %s\n", str);
	
	reverse_sentence_1(str);
	
	printf("after 1--> %s\n", str);
	
	reverse_sentence(str);
	printf("after 2--> %s\n", str);
	return 0;
}

bool reverse_sentence_1(char str[])
{
	int len = strlen(str);
	int pos = len - 1;
	int word_start;
	int word_end;
	int write_pos = 0;
	
	char* buf = (char*)malloc(len + 1);
	if (buf == NULL)
		return false;
	
	while (pos >= 0)
	{
		if (str[pos] == ' ')
		{
			buf[write_pos++] = ' ';
		}
		else
		{
			word_end = pos;
			while (pos >= 0 && str[pos] != ' ')
				pos--;
			pos++;
			word_start = pos;
			while (word_start <= word_end)
			{
				buf[write_pos++] = str[word_start++];
			}
		}
		pos--;
	}
	buf[write_pos] = '\0';
	strcpy(str, buf);
	free(buf);
	return true;
}

void reverse_string(char str[], int start, int end)
{
	while (start < end)
	{
		char c = str[start];
		str[start] = str[end];
		str[end] = c;
		
		start++;
		end--;
	}
}


void reverse_sentence(char str[])
{
	int len = strlen(str);
	int word_start, pos;
	
	reverse_string(str, 0, len - 1);
	
	for (pos = 0; pos < len; pos++)
	{
		if (str[pos] != ' ')
		{	
			word_start = pos;
			while (pos < len && 
				str[pos] != ' ')
				pos++;
			pos--;
			reverse_string(str, word_start, pos);
		}
	}
}