高精度加法

重点
1. 模拟加法运算过程
2. t表示进位，开始进位为0
3. 最后判断进位不为0，则需要加入c中

#include <iostream>
#include <cstring>
#include <algorithm>
#include <vector>

using namespace std;
const int N = 1000010;

vector<int> add(vector<int> &a, vector<int> &b) {
    vector<int> c;
    int t = 0;
    for (int i = 0; i < a.size() || i < b.size(); i++) {
        if (i < a.size()) t += a[i];
        if (i < b.size()) t += b[i];
        c.push_back(t % 10);
        t /= 10;
    }
    if (t > 0) c.push_back(t);
    return c;
}

int main() {
    string s1, s2;
    cin >> s1 >> s2;
    vector<int> a, b;
    for (int i = s1.size() - 1; i >= 0; i--) a.push_back(s1[i] - '0');
    for (int i = s2.size() - 1; i >= 0; i--) b.push_back(s2[i] - '0');

    auto c = add(a, b);
    for (int i = c.size() - 1; i >= 0; i--) printf("%d", c[i]);

    return 0;
}