interviews/training->training

puzzles/training/string_addition.cpp

@@ -0,0 +1,84 @@
+/*
+VIM: let b:lcppflags="-std=c++14 -O2 -pthread -I."
+VIM: let b:wcppflags="/O2 /EHsc /DWIN32"
+*/
+#include "stdafx.h"
+#include <iostream>
+#include <exception>
+#include <string>
+#include <chrono>
+#include <vector>
+#include <algorithm>
+#include <queue>
+#include <mutex>
+#include <condition_variable>
+#include <atomic>
+
+/*
+	given an array representing a non-negative integer (ex: 123 represented
+	as [1,2,3]), return the next integer (output: [1,2,4]).
+	run through all edge cases (ex: [9,9,9,9,9,9,9,9] etc)
+*/
+
+int dig(char ch) {
+	return ch - '0';
+}
+
+char chr(int dig) {
+	return dig + '0';
+}
+
+std::string incr(std::string n) {
+	int carry = 1;
+	for (size_t i = n.size(); i-- > 0; ) {
+		int ds = dig(n[i]) + carry;
+		if (ds >= 10) {
+			carry = ds / 10;
+			ds %= 10;
+		}
+		else {
+			carry = 0;
+		}
+		n[i] = chr(ds);
+	}
+
+	if (carry) {
+		return chr(carry) + n;
+	}
+	else {
+		return n;
+	}
+}
+
+int main()
+{
+	try {
+		auto begin = std::chrono::high_resolution_clock::now();
+
+		std::cout << incr("0") << std::endl;
+		std::cout << incr("1") << std::endl;
+		std::cout << incr("9") << std::endl;
+		std::cout << incr("10") << std::endl;
+		std::cout << incr("15") << std::endl;
+		std::cout << incr("19") << std::endl;
+		std::cout << incr("99") << std::endl;
+		std::cout << incr("9999999") << std::endl;
+
+		auto end = std::chrono::high_resolution_clock::now();
+		std::chrono::duration<double> seconds = end - begin;
+		std::cout << "Time: " << seconds.count() << std::endl;
+		return 0;
+	}
+	catch (const std::exception& e)
+	{
+		std::cerr << std::endl
+			<< "std::exception(\"" << e.what() << "\")." << std::endl;
+		return 2;
+	}
+	catch (...)
+	{
+		std::cerr << std::endl
+			<< "unknown exception." << std::endl;
+		return 1;
+	}
+}