65. Valid Number

validNumber.cpp

/*
Validate if a given string is numeric.

Some examples:
"0" => true
" 0.1 " => true
"abc" => false
"1 a" => false
"2e10" => true

Note: It is intended for the problem statement to be ambiguous. You should gather all requirements up front before implementing one.

Update (2015-02-10):
The signature of the C++ function had been updated. If you still see your function signature accepts a const char * argument, please click the reload button to reset your code definition.

Copyright © 2018 LeetCode
*/

#include "stdafx.h"
#include <iostream>
#include <functional>

#include <cctype>
#include <algorithm>

bool isNumber(std::string s) {

	//trim L
	s.erase(s.begin(), std::find_if(s.begin(), s.end(), [](int ch) {
		return !std::isspace(ch);
	}));

	//trim R
	s.erase(std::find_if(s.rbegin(), s.rend(), [](int ch) {
		return !std::isspace(ch);
	}).base(), s.end());

	if (s.length() == 0)
		return false;

	bool prevDigit = false;
	bool nextDigitRequired = false;
	bool expanentaMode = false;
	bool onlyOneDotAllowed = false;
	bool onlyOneSignAllowed = false;

	for (auto &c : s) {
		bool isDigit = std::isdigit(c) != 0;
		bool isSpace = std::isspace(c) != 0;
		bool isDot = c == '.';
		bool isExpanenta = c == 'e';
		bool isMunus = c == '-';
		bool isPlus = c == '+';
		
		if (isDigit) {
			prevDigit = true;
			nextDigitRequired = false;
			continue;
		}

		if (isDot && !onlyOneDotAllowed && !expanentaMode) {
			nextDigitRequired = !prevDigit;
			onlyOneDotAllowed = true;
			continue;
		}

		// Epanenta mode allows plus or minus inside of experession
		if (expanentaMode && (isPlus || isMunus) && !onlyOneSignAllowed) {
			nextDigitRequired = true;
			onlyOneSignAllowed = true;
			continue;
		}

		if (nextDigitRequired) {
			return false;
		}

		if (isMunus || isPlus) {
			nextDigitRequired = true;
			if (prevDigit) {
				return false;
			}
			continue;
		}

		if (isExpanenta && prevDigit && !expanentaMode) {
			expanentaMode = true;
			nextDigitRequired = true;
			continue;
		}


		return false;
	}
	if (nextDigitRequired) {
		return false;
	}

	return true;
}


void checkValue(std::string input, bool expected)
{
	auto result = isNumber(input);
	if (result != expected) {
		throw new std::runtime_error("Failed on \"" + input + "\" Expected: " + (expected ? "(True)" : "(False)"));
	}
}

int main()
{
	// Default from task
	checkValue("0", true);
	checkValue(" 0.1", true);
	checkValue("abc", false);
	checkValue("1 a", false);
	checkValue("2e10", true);
		
	// Addtional checks
	checkValue("", false);
	checkValue(" ", false);
	checkValue("2e10 ", true);
	checkValue("2e10e2", false);
	checkValue("2e", false);
	checkValue("1 ", true);
	checkValue(".1", true);
	checkValue("3.", true);
	checkValue("..2", false);
	checkValue("1 4", false);
	checkValue("1  4", false);
	checkValue("1..4", false);
	checkValue("1  ", true);
	checkValue(" .9", true);
	checkValue("-9", true);
	checkValue(" -9.0", true);
	checkValue("3-2", false);
	checkValue("0- ", false);
	checkValue("+1", true);
	checkValue(" +.8", true);
	checkValue("1e.", false);
	checkValue(".-4", false);
	checkValue("6e6.5", false);
	checkValue(" 005047e+6", true);
	checkValue("459277e38+", false);
	checkValue("2e+60++604", false);
	checkValue("32.e-80123", true);

	std::cout << "Success!" << std::endl;
  return 0;
}