scanf 쓰다가 cin을 쓰면 형식에 맞춰서 input을 받는 게 되게 어려운데, 헤더에 코드 몇 줄만 추가해주면 쉽게 할 수 있음.

#include <iostream>
#include <cstring>

//These are handy bits that go in a header somewhere
template<class e, class t, int N>
std::basic_istream<e,t>& operator>>(std::basic_istream<e,t>& in, const e(&sliteral)[N]) {
        e buffer[N-1] = {}; //get buffer
        in >> buffer[0]; //skips whitespace
        if (N>2)
                in.read(buffer+1, N-2); //read the rest
        if (strncmp(buffer, sliteral, N-1)) //if it failed
                in.setstate(std::ios::failbit); //set the state
        return in;
}
template<class e, class t>
std::basic_istream<e,t>& operator>>(std::basic_istream<e,t>& in, const e& cliteral) {
        e buffer(0);  //get buffer
        in >> buffer; //read data
        if (buffer != cliteral) //if it failed
                in.setstate(std::ios::failbit); //set the state
        return in;
}
//redirect mutable char arrays to their normal function
template<class e, class t, int N>
std::basic_istream<e,t>& operator>>(std::basic_istream<e,t>& in, e(&carray)[N]) {
        return std::operator>>(in, carray);
}

이 코드를 컴퓨터 어딘가에 저장해놓고 include해서 쓰셈.
사용법은 다음과 같음.

int main(void)
{
	int x,y;
	std::cout << "Input coordinate(ex: x=12,y=15):";
	std::cin >> 'x' >> '=' >> x >> ',' >> 'y' >> '=' >> y; //whitespace between format characters are allowed when skipws is set; e.g x = 12, y = 15 is allowed
	std::cout << x << ", " << y << '\n';
	std::cout << "Input coordinate again without whitespace(ex: x=12,y=15):";
	std::cin >> "x=" >> x >> ",y=" >> y; //whitespace between format characters are NOT allowed regardless of skipws flag; e.g x = 12, y = 15 is NOT allowed, only x=12,y=15 is allowed
	if(std::cin.fail())
	{
		std::cout << "DONT PUT WHITE SPACE!\n";
		return -1;
	}
	std::cout << x << ", " << y << '\n';
	return 0;
}

입력:
x = 12, y = 15
x=12,y=15
출력:
12, 15
12, 15

입력:
x = 12, y = 15
x = 12, y = 15
출력:
12, 15
DONT PUT WHITE SPACE!

물론 입력 형식이 복잡해지면 정규표현식을 써야겠지만 간편하게 써먹기엔 꽤 좋은 코드임.
출처:https://stackoverflow.com/questions/17244181/reading-formatted-input-using-c-streams/17244442?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa