题解 | 高精度整数加法

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

int main() {
    string a, b;
    cin >> a >> b;
    int n = a.size(), m = b.size();
    if (n <= m) {
        int p = n, q = m;
        int carry = 0;
        string res = "";
        while (p) {
            int sum = a[--p] - '0' + b[--q] - '0' + carry;
            if (sum > 9) {
                sum = sum % 10;
                carry = 1;
            } else {
                carry = 0;
            }
            res = to_string(sum) + res;
        }
        while (q) {
            int sum = b[--q] - '0' + carry;
            if (sum > 9) {
                sum = sum % 10;
                carry = 1;
            } else {
                carry = 0;
            }
            res = to_string(sum) + res;
        }
        if (carry) res = to_string(carry) + res;
        cout << res << endl;
    } else {
        int p = n, q = m;
        int carry = 0;
        string res = "";
        while (q) {
            int sum = a[--p] - '0' + b[--q] - '0' + carry;
            if (sum > 9) {
                sum = sum % 10;
                carry = 1;
            } else {
                carry = 0;
            }
            res = to_string(sum) + res;
        }
        while (p) {
            int sum = a[--p] - '0' + carry;
            if (sum > 9) {
                sum = sum % 10;
                carry = 1;
            } else {
                carry = 0;
            }
            res = to_string(sum) + res;
        }
        if (carry) res = to_string(carry) + res;
        cout << res << endl;
    }


    return 0;
}
// 64 位输出请用 printf("%lld")