student a am i -> i am a student

//student a am i  -> i am a student
#include<stdio.h>
#include<assert.h>
void reverse(char* start, char* end){
	assert(start);
	assert(end);
	char tmp = 0;
	while (start < end){
		tmp = *start;
		*start = *end;
		*end = tmp;
		start++;
		end--;
	}
}
void reverse_str(char arr[]){
	assert(arr);
	char *p_arr = NULL;
	while (*arr != '\0'){
		p_arr = arr;
		while (*arr != ' ' && *arr != '\0'){
			arr++;
		}
		reverse(p_arr, arr - 1);
		if (*arr!='\0')
			arr++;
	}
}

int main(){
	char arr[] = "student a am i";
	int size = sizeof(arr) / sizeof(arr[0]) - 2;
	reverse(arr, arr+size);
	reverse_str(arr,arr+size);
	printf("%s\n",arr);
	system("pause");
	return 0;
}