3.5.3 指针和数组

练习3.34

	int main() {
		
		int ia[] = { 1,2,3,4,5 };
		int* p1 = &ia[0];
		int* p2 = &ia[2];
		cout << *p1 << endl; //1
		cout << *p2 << endl; //3
		p1 += p2 - p1;       //实质等价于 p1=p1+(p2-p1)，让p1指向p2所指的对象
		cout << *p1 << endl; //3
		cout << *p2 << endl; //3

}

练习3.35

	int main() {
		
		int ia[] = { 1,2,3,4,5 };
		
		int* pbeg =ia, * pend = end(ia);
		while (pbeg != pend)
		{
			*pbeg = 0;
			cout << *pbeg << " ";
			++pbeg;
		}
}

练习3.36

	int main() 
	{
		
		int ia[] = { 1,2,3,4,5 };
		int ib[] = { 1,2,5,4,5,6,7 };
		
		if (ia == ib)
		{
			cout << "相等" << endl;
		}
		else
			cout << "不相等" << endl;
     }

int main() 
	{
		
		int ia[] = { 1,2,3,4,5 };
		int ib[] = { 1,2,5,4,4 };
		

		int* ba =ia, * ea = end(ia);
		int* bb = ib, * eb = end(ib);
		
		
		//比较ia数组和ib数组是否相等
		while (*ba == *bb && ba != ea && bb != eb) //验证元素是否相同，如果全部检查完则结束循环
		{
			
			++ ba; 
			++ bb;
		}
		//此时有2种情况
		//ba和bb不相等，第一个循环条件不满足，中途退出循环，此时*ba！=*bb
		//ba和bb前面都相等，ba和bb都到了最后一个元素也相等，++后得到尾元素的后一个位置，第二个和第三个循环条件不满足，退出循环
        //ba和bb前面都相等，ba到了最后一个元素，而bb没到，第二个循环条件不满足，此时*ba！=*bb

		if (*ba == *bb)
		{
			cout << "相等" << endl;
		}
		else {
			cout << "不相等" << endl;
		}
	
     }

int main() 
	{
		
		vector<int> ia = { 1,2,3,4,5 };
		vector<int> ib = { 1,2,5,4,4 };
		
		if (ia == ib)
		{
			cout << "相等" << endl;
		}
		else
			cout << "不相等" << endl;
	
     }