题解 | A+B

#include <iostream>//数据范围不大，用long long直接可以，练习一下高精度加减法
#include <algorithm>
#include <cmath>
#include <cstring>
#include <string>
using namespace std;


string Add(string s1, string s2) {
    int l1 = s1.size(), l2 = s2.size();
    if (l1 < l2)swap(s1, s2);
    reverse(s1.begin(), s1.end());
    reverse(s2.begin(), s2.end());
    int car = 0;
    string s = "";
    for (int i = 0; i < s2.size(); i++) {
        int num = (s1[i] - '0') + (s2[i] - '0') + car;
        car = num / 10;
        char c = num % 10 + '0';
        s = s + c;
    }
    for (int i = s2.size(); i < s1.size(); i++) {
        int num = (s1[i] - '0') +  car;
        car = num / 10;
        char c = num % 10 + '0';
        s = s + c;
    }
    if (car)s = s + "1";
    reverse(s.begin(), s.end());
    while (s[0] == '0')s.erase(0, 1);
    if (s == "")s = "0";
    return s;

}

bool cmp(string s1, string s2) {
    int l1 = s1.size(), l2 = s2.size();
    if (l1 < l2)return false;
    else if (s1 < s2)return false;
    return true;
}

string Sub(string s1, string s2) {
    int l1 = s1.size(), l2 = s2.size();
    if (l1 < l2)swap(s1, s2);
    else if (s1 < s2)swap(s1, s2);
    reverse(s1.begin(), s1.end());
    reverse(s2.begin(), s2.end());
    int car = 0;
    int ans[l1+2];
    string s = "";
    memset(ans, 0, sizeof(ans));
    for (int i = 0; i < s2.size(); i++) {
        ans[i] += (s1[i] - s2[i]);
        if (ans[i] < 0) {
            ans[i + 1] -= 1;
            ans[i] += 10;
        }
        char c = ans[i] + '0';
        s = s + c;
    }
    for (int i = s2.size(); i < s1.size(); i++) {
        ans[i] += s1[i] - '0';
        char c = ans[i] + '0';
        s = s + c;
    }
    if(ans[s1.size()]!=0){
        char c = ans[s1.size()] + '0';
        s = s + c;
    }
    reverse(s.begin(), s.end());
    while (s[0] == '0')s.erase(0, 1);
    if (s == "")s = "0";
    return s;
}



int main() {
    string A, B;
    while (cin >> A >> B) {
        for (int i = 0; i < A.size(); i++) {
            if (A[i] == ',') {
                A.erase(i, 1);
                i--;
            }
        }
        //    cout << A << endl;
        for (int i = 0; i < B.size(); i++) {
            if (B[i] == ',') {
                B.erase(i, 1);
                i--;
            }
        }
        if (A[0] != '-' && B[0] != '-')cout << Add(A, B) << endl;
        else if (A[0] == '-' && B[0] == '-') {
            A.erase(0, 1);
            B.erase(0, 1);
            cout << "-" << Add(A, B) << endl;
        } else {
            if (A[0] == '-') {
                A.erase(0, 1);
                if (cmp(A, B)) {
                    cout << "-" << Sub(A, B) << endl;
                } else cout << Sub(A, B) << endl;
            } else {
                B.erase(0, 1);
                if (cmp(A, B)==false) {
                    cout << "-" << Sub(A, B) << endl;
                } else cout << Sub(A, B) << endl;
            }
        }
        
        //    cout << B << endl;
        // string ans = Add(A,B);
        // cout<<ans<<endl;
        //     cout<<Sub("234567890","123456789")<<endl;

    }
   // cout<<Sub("386" ,"4508")<<endl;
}
// 64 位输出请用 printf("%lld")