casbin/util/set_subtract.cpp

/*
 * Copyright 2020 The casbin Authors. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "casbin/pch.h"

#ifndef SET_SUBSTRACT_CPP
#define SET_SUBSTRACT_CPP

#include <unordered_map>

#include "casbin/util/util.h"

namespace casbin {

// SetSubtract returns the elements in `a` that aren't in `b`.
std::vector<std::string> SetSubtract(const std::vector<std::string>& a, const std::vector<std::string>& b) {
    std::unordered_map<std::string, bool> mb;
    mb.reserve(b.size());

    for (const std::string& it : b)
        mb[it] = true;

    std::vector<std::string> diff;
    diff.reserve(a.size());

    for (const std::string& it : a)
        if (!mb[it])
            diff.push_back(it);

    return diff;
}

} // namespace casbin

#endif // SET_SUBSTRACT_CPP