HeapSort.cpp

void PushDown(int* numbers, int length, int index) {
    int value = numbers[index];
    while(index*2+1 < length) {
        int t = index;
        if(index*2+1 < length && numbers[index*2+1] > value) {
            t = index * 2 + 1;
        }
        if(index*2+2 < length && numbers[index*2+2] > (t==index)? value : numbers[t]) {
            t = index * 2 + 2;
        }
        if(t == index) {
            numbers[index] = value;
            break;
        } else {
            numbers[index] = numbers[t];
            index = t;
        }
    }
    if(index*2+1 >= length) numbers[index] = value;
}

void BuildHeap(int* numbers, int length) {
    for(int i = length/2-1; i >= 0; --i) {
        HeapDown(numbers, length, i);
    }
}

void HeapSort(int* numbers, int length) {
    if(numbers == NULL || length <= 1) return;
    BuildHeap(numbers, length);
    int tmp = numbers[0];
    numbers[0] = numbers[length-1];
    numbers[length-1] = tmp;
    length -= 1;
    while(length > 1) {
        PushDown(numbers, length, 0);
        tmp = numbers[0];
        numbers[0] = numbers[length-1];
        numbers[length-1] = tmp;
        length -= 1;
    }
}

SelectionSort.cpp

void SelectSort(int* numbers, int length) {
    if(numbers == NULL || length <= 1) return;
    for(int i = 0; i < length; ++i) {
        int _min = numbers[i];
        int _ind = i;
        for(int j = i+1; j < length; ++j) {
            if(numbers[j] < _min) {
                _min = numbers[j];
                _ind = j;
            }
        }
        if(_ind != i) {
            numbers[_ind] = numbers[i];
            numbers[i] = _min;
        }
    }
}