ok i'm back: 210-course-schedule-ii, 43-multiply-strings

43-multiply-strings/driver.cpp

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+#include "soln.hpp"
+
+int main()
+{
+	string num1 = "123", num2 = "456", answer = "56088";
+	Solution soln;
+	cout << "Multiplied strings correctly? " << soln.test(num1, num2, answer) << endl;
+	return 0;
+}

43-multiply-strings/soln.cpp

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+#include "soln.hpp"
+
+string Solution::multiply(string num1, string num2)
+{
+	// product can't have more digits than sum of individual num's digits
+	string prod(num1.size() + num2.size(), '0');
+	int carry, tmp;
+
+	// standard multiplication
+	// one digit of num1 with all of num2, accumulate
+	for (int i = num1.size() - 1; i >= 0; i--)
+	{
+		carry = 0;
+		for (int j = num2.size() - 1; j >= 0; j--)
+		{
+			tmp = (num1[i] - '0') * (num2[j] - '0') + (prod[i + j + 1] - '0') + carry;
+			prod[i + j + 1] = (tmp % 10) + '0';
+			carry = tmp / 10;
+		}
+		prod[i] += carry;
+	}
+
+	// strip leading zeroes
+	int start_pos = prod.find_first_not_of("0");
+	if (start_pos != -1)
+		return prod.substr(start_pos);
+	return "0";
+}
+
+bool Solution::test(string num1, string num2, string answer)
+{
+	return multiply(num1, num2) == answer;
+}

43-multiply-strings/soln.hpp

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+#include <bits/stdc++.h>
+using namespace std;
+class Solution
+{
+public:
+	string multiply(string num1, string num2);
+	bool test(string num1, string num2, string answer);
+};