#include <bits/stdc++.h>
using namespace std;
int a[10100],b[10100],c[10100];
int main() {
    string A,B;
    cin>>A>>B;
    int n;
    int len = (A.length()>=B.length())?A.length():B.length();
    for (int i = A.length() - 1, j = 1; i >= 0; i--, j++) a[j] = A[i] - '0';
    for (int i = B.length() - 1, j = 1; i >= 0; i--, j++) b[j] = B[i] - '0';
    for (int i=1;i<=len;i++)
    {
        c[i] += (a[i]-b[i]);
        if(c[i] < 0)
        {
            a[i+1]-=1;
            c[i]+=10;
        } 
    }
    int len2;
    for(len2 =1;len2>=len;len2++) if(c[len2]!=0) break;
    for (int i = len-1; i >= len2; i--) cout << c[i];
    return 0;
}

P2142 高精度减法这道题目求各位大佬讲解一下