python/TangDou/LuoGuBook/P2142.cpp

#include <bits/stdc++.h>

using namespace std;

/**
 * 功能：高精度减法模板
 * @param A
 * @param B
 * @return
 */
vector<int> sub(vector<int> &A, vector<int> &B) {
    int t = 0;
    vector<int> C;
    for (int i = 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();
    return C;
}

//对比函数
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--)  //这里的判断要注意顺序，因为高位在后
        if (A[i] != B[i]) return A[i] > B[i];
    return true;
}

int main() {
    //以字符串形式读入
    string a, b;
    cin >> a >> b;
    vector<int> A, B, C;
    //1、准备动作，将字符串的每一位，反序放入到整数运算数组中
    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');
    //2、调用模板进行计算
    if (cmp(A, B)) C = sub(A, B);
    else {
        printf("-");
        C = sub(B, A);
    }
    //3、输出结果,需要倒序噢
    for (int i = C.size() - 1; i >= 0; i--)printf("%d", C[i]);
    return 0;
}