solidity/libdevcore/StringUtils.cpp

/*
	This file is part of solidity.

	solidity is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	solidity is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
*/
/** @file StringUtils.h
 * @author Balajiganapathi S <balajiganapathi.s@gmail.com>
 * @date 2017
 *
 * String routines
 */

#include "StringUtils.h"
#include <algorithm>
#include <string>
#include <vector>

using namespace std;
using namespace dev;

bool dev::stringWithinDistance(string const& _str1, string const& _str2, size_t _maxDistance)
{
	if (_str1 == _str2)
		return true;

	size_t n1 = _str1.size();
	size_t n2 = _str2.size();
	size_t distance = stringDistance(_str1, _str2);

	// if distance is not greater than _maxDistance, and distance is strictly less than length of both names, they can be considered similar
	// this is to avoid irrelevant suggestions
	return distance <= _maxDistance && distance < n1 && distance < n2;
}

size_t dev::stringDistance(string const& _str1, string const& _str2)
{
	size_t n1 = _str1.size();
	size_t n2 = _str2.size();
	// Optimize by storing only last 2 rows and current row. So first index is considered modulo 3
	// This is a two-dimensional array of size 3 x (n2 + 1).
	vector<size_t> dp(3 * (n2 + 1));

	// In this dp formulation of Damerau–Levenshtein distance we are assuming that the strings are 1-based to make base case storage easier.
	// So index accesser to _name1 and _name2 have to be adjusted accordingly
	for (size_t i1 = 0; i1 <= n1; ++i1)
		for (size_t i2 = 0; i2 <= n2; ++i2)
		{
			size_t x = 0;
			if (min(i1, i2) == 0) // base case
				x = max(i1, i2);
			else
			{
				size_t left = dp[(i1 - 1) % 3 + i2 * 3];
				size_t up = dp[(i1 % 3) + (i2 - 1) * 3];
				size_t upleft = dp[((i1 - 1) % 3) + (i2 - 1) * 3];
				// deletion and insertion
				x = min(left + 1, up + 1);
				if (_str1[i1-1] == _str2[i2-1])
					// same chars, can skip
					x = min(x, upleft);
				else
					// different chars so try substitution
					x = min(x, upleft + 1);

				// transposing
				if (i1 > 1 && i2 > 1 && _str1[i1 - 1] == _str2[i2 - 2] && _str1[i1 - 2] == _str2[i2 - 1])
					x = min(x, dp[((i1 - 2) % 3) + (i2 - 2) * 3] + 1);
			}
			dp[(i1 % 3) + i2 * 3] = x;
		}

	return dp[(n1 % 3) + n2 * 3];
}

string dev::quotedAlternativesList(vector<string> const& suggestions)
{
	vector<string> quotedSuggestions;

	for (auto& suggestion: suggestions)
		quotedSuggestions.push_back("\"" + suggestion + "\"");

	return joinHumanReadable(quotedSuggestions, ", ", " or ");
}