solution in c

[okhaifo]

//is number

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

typedef struct _node node;
struct _node{
int val;
char other;
node next;
};
node init();
void initNodes();
int isNumber(char* num);

node *head;

void initNodes(){
head = init();
head->next = init();
head->val = 0.0; //just a sample value not necessary
head->next = head;
}

node* init(){
node* val = (node *) malloc(sizeof(node));
return val;
}

int isNumber(char* num){
//parser
initNodes();
int i = 0;
while(num[i] !=0x0){
printf("parser %c\n", num[i]);

	if(num[i] >='0' && num[i] <= '9'){
		node *newn = init();
		newn->val = num[i]-'0';
		newn->next = head->next;
		head->next = newn;
	}
	else{
		node *newn = init();
		newn->other = num[i];
		newn->val =-1;
		newn->next = head->next;
		head->next = newn;
	}
	i++;
}
//going through each node
node* retri = init();
retri = head->next;
while(retri != head){
	//checker
	printf("retreive value is %d\n",retri->val);
	if(retri->val >=0 && retri->val <= 9 ){
		
		retri = retri->next;
	}
	else if(retri->val == -1){
		//check if point or e
		if(retri->other =='.' || retri->other=='e' || retri->other=='E'){
			retri = retri->next;
		}
		else{
			return 0;
		}
	}
	else{
		return 0;
	}
}
return 1;

}

int main(void){
printf("is it a number: %s\n",isNumber("2e10") ? "true":"false");
return 0;
}