high_precision_sub.cpp

#include <iostream>
#include <vector>
using namespace std;

bool cmp(vector<int>& A, vector<int>& B) {
	if (A.size() != B.size()) return A.size() > B.size();
	for (int i = A.size() - 1; i >= 0; i--) {
		if (A[i] != B[i]) 
			return A[i] > B[i];
	}
	return true;
}

vector<int> sub(vector<int>& A, vector<int>& B) {
	vector<int> C;
	for (int i = 0, t = 0; i < A.size(); i++) {
		t = A[i] - t;
		if (i < B.size()) t -= B[i];
		C.push_back((t + 10) % 10);
		if (t < 0) t = 1;
		else t = 0;
	}

	while (C.size() > 1 && C.back() == 0) C.pop_back(); // È¥µôÇ°µ¼0
	return C;
}

int main()
{
	string a, b;
	vector<int> A, B;
	cin >> a >> b;
	for (int i = a.size() - 1; i >= 0; i--) A.push_back(a[i] - '0');
	for (int i = b.size() - 1; i >= 0; i--) B.push_back(b[i] - '0');

	if (cmp(A, B)) {
		auto C = sub(A, B);
		for (int i = C.size() - 1; i >= 0; i--) printf("%d", C[i]);
	}
	else {
		auto C = sub(B, A);
		printf("-");
		for (int i = C.size() - 1; i >= 0; i--) printf("%d", C[i]);
	}
	return 0;
}