Heap

template<typename T>
struct Heap {

    explicit Heap(size_t size) {
        _Size = size;
        try {
            _Tree = (T *) malloc( _Size * sizeof(T));
        }
        catch(...){
            std::cerr << "NOMEM" ;
            exit(1);
        }
    }

    Heap() {
        try {
            _Tree = (T *) malloc( _Size * sizeof(T));
        }
        catch(...){
            std::cerr << "NOMEM" ;
            exit(1);
        }
    }

    inline bool is_empty() {
        return _elemSize == 0;
    }

    T top() {
        try{
            if (is_empty()){
                throw;
            }
            return _Tree[0];
        }
        catch (...){
            std::cerr << "Err: Heap is empty" << '\n';
        }

    }

    void push(T value) {
        if (_elemSize == _Size) {
            _resize();
        }
        _Tree[_elemSize++] = value;
        siftUp(_elemSize - 1);
    }

    void pop() {
        if (!is_empty()) {
            _Tree[0] = _Tree[--_elemSize];
            siftDown(0);
        } else {
            std::cerr << "Err: Heap is empty" << '\n';
        }

    }

    void clear() {
            _elemSize = 0;
    }


    ~Heap() {
        free(_Tree);
    }

private:
    T *_Tree;
    size_t _elemSize = 0;
    size_t _Size = 4;

    void siftUp(size_t index) {
        while (index > 0 && _Tree[index] > _Tree[(index - 1) / 2]) {
            std::swap(_Tree[index], _Tree[(index - 1) / 2]);
            index = (index - 1) / 2;
        }
    }

    void siftDown(size_t index) {
        while (2 * index + 1 < _elemSize) {
            size_t lch = 2 * index + 1;
            size_t rch = 2 * index + 2;
            size_t maxCh = lch;
            if (rch < _elemSize && _Tree[rch] > _Tree[maxCh]) {
                maxCh = rch;
            }
            if (_Tree[index] >= _Tree[maxCh])
                return;
            std::swap(_Tree[index], _Tree[maxCh]);
            index = maxCh;
        }
    }

    void _resize() {
        try {
            _Tree = (T *) realloc(_Tree, _Size * 2 * sizeof(T));
            _Size *= 2;
        }
        catch(...){
            std::cerr << "NOMEM" ;
            exit(1);
        }
    }
};