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

char house[]="this is a test string";

int main(){

	int len = strlen(house);

	char *buff = (char*)malloc(len+1);
	memset(buff,'\0',len * sizeof(char)+1);

	char* end = (house+len);
	char* beg = (house+len);

	int j = 0;
	for(int i = 0; i < strlen(house)+1; i++){
		beg--;
		if(*beg == ' ' || beg < house){

			char* tmp = beg;
			tmp++;
			while(tmp != end){
				buff[j++] = *tmp++;
			}

			buff[j++]=' ';
			end = beg;
		}
	}

printf("%s\n",buff);

return 0;

}