大数相乘

#include <iostream>  #include <vector>#include <string>using namespace std;int main(){string s1, s2;while (cin >> s1 >> s2) {vector<int> v1, v2;for (size_t i = 0; i != s1.size(); ++i)v1.push_back((int)(s1[s1.size() - 1 - i]) - '0');for (size_t j = 0; j != s2.size(); ++j)v2.push_back((int)(s2[s2.size() - 1 - j]) - '0');vector<int> res(v1.size() + v2.size(), 0);for (size_t i = 0; i != v1.size(); ++i) {for (size_t j = 0; j != v2.size(); ++j) {int k = i + j;res[k] += v1[i] * v2[j];while (res[k] > 9) {res[k + 1] += res[k] / 10;res[k] %= 10;++k;}}}int len = res.size() - 1;while (len > 0 && res[len] == 0)--len;for (int i = len; i >= 0; --i)cout << res[i];cout << endl;}return 0;}