AcWing_792 高精度减法

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

vector<int> A, B;
string a, b;

bool cmp(vector<int> &A, vector<int> &B){
    int sA = (int)A.size(), sB = (int)B.size();
    if(sA != sB) return sA > sB;
    
    for(int i = sA - 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;
    int t = 0;
    int sA = (int)A.size(), sB = (int)B.size();
    
    for(int i = 0; i <= sA - 1; i ++){
        t = A[i] - t;
        if(i <= sB - 1) t -= B[i];
        C.push_back((t + 10) % 10);
        if(t < 0) t = 1;
        else t = 0;
    }
    
    while((int)C.size() >= 2 && !C.back()) C.pop_back();
    
    return C;
}

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    
    cin >> a >> b;
    int sa = (int)a.size(), sb = (int)b.size();
    for(int i = sa - 1; i >= 0; i --) A.push_back(a[i] - '0');
    for(int i = sb - 1; i >= 0; i --) B.push_back(b[i] - '0');
    
    vector<int> C;
    if(cmp(A, B)) C = sub(A, B);
    else C = sub(B, A), cout << '-';
    
    int sC = (int)C.size();
    for(int i = sC - 1; i >= 0; i --) cout << C[i];
    
    return 0;
}