43. 字符串相乘(LeetCode中等)(高精度)

43. 字符串相乘

class Solution {
public:
    string multiply(string num1, string num2) {
        vector<int> A, B;
        int n = num1.size(), m = num2.size();
        for(int i = n - 1; i >= 0; --i) A.push_back(num1[i] - '0');
        for(int i = m - 1; i >= 0; --i) B.push_back(num2[i] - '0');
        vector<int> C(n + m);
        for(int i = 0; i < n; ++i){
            for(int j = 0; j < m; ++j){
                C[i+j] += A[i] * B[j];
            }
        }
        for(int i = 0, t = 0; i < C.size(); ++i){
            t += C[i];
            C[i] = t % 10;
            t /= 10;
        }
        
        int k = C.size() - 1;
        while(k > 0 && !C[k]) k--;
        string res = "";
        while(k >= 0) res += C[k--] + '0';

        return res;
    }
};