realloc動態數組以及作用域

#include <stdlib.h>
#include <stdio.h>
#define SIZE 20
int *p ;
int m = SIZE;
int n = 0;//多少個元素
int main(){
	p = malloc(SIZE);
	scan_input();
	printArray();
	free(p);
	return 0;
}
void scan_input(){
	//scanf("%d",p[]);
	int i =0;
	while(1){
		
		if(i>=m/4){//int 類型所以除以4
			//relloc
			m = m*2;//一次性擴大兩倍
			printf("%s","realloc...");
			p = realloc(p,m);
		}
		
		scanf("%d",&p[i]);
		if(p[i] == -1){
			break;
		}
		i++;
		n++;
		
	}
	return ;
}
void printArray(){
	int i;
	for(i=0;i<n;i++){
		printf("%d\n",p[i]);
	}
	return ;
}