LeetCode: Multiply Strings

一点小失误，少数次过

class Solution {
public:
    string multiply(string num1, string num2) {
        vector<int> mul(num1.size() + num2.size());
        for (int i = 0; i < num1.size(); i++) {
            for (int j = 0; j < num2.size(); j++) {
                mul[num1.size()-1-i+num2.size()-1-j] += (num1[i] - '0') * (num2[j] - '0');
            }
        }
        int carry = 0;
        for (int i = 0; i < mul.size(); i++) {
            mul[i] += carry;
            carry = mul[i] / 10;
            mul[i] %= 10;
        }
        string ans;
        for (int i = mul.size()-1; i >= 0; i--) {
            if (mul[i] == 0) {
                if (ans.size() > 0) ans += ('0' + mul[i]);
            }
            else ans += ('0' + mul[i]);
        }
        return ans.size() == 0? "0" : ans;
    }
};

 C#

public class Solution {
    public string Multiply(string num1, string num2) {
        int[] mul = new int[num1.Length + num2.Length];
        for (int i = 0; i < num1.Length; i++) {
            for (int j = 0; j < num2.Length; j++) {
                mul[num1.Length-1-i+num2.Length-1-j] += (num1[i] - '0') * (num2[j] - '0');
            }
        }
        int c = 0;
        for (int i = 0; i < mul.Length; i++) {
            mul[i] += c;
            c = mul[i] / 10;
            mul[i] %= 10;
        }
        string ans = "";
        for (int i = mul.Length-1; i >= 0; i--) {
            if (mul[i] == 0) {
                if (ans.Length > 0) ans += mul[i];
            }
            else ans += mul[i];
        }
        return ans.Length == 0? "0" : ans;
    }
}