54 lines
1.8 KiB
C++
54 lines
1.8 KiB
C++
#include <algorithm>
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#include <iostream>
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#include <vector>
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std::vector<std::size_t> getReversalsToSort(const std::vector<int> &arr);
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/**
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* Imagine a sort algorithm, that sorts array of integers by repeatedly
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* reversing the order of the first several elements of it.
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*
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* For example, to sort [12,13,11,14], you need to reverse the order of the
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* first two (2) elements. You will get [13,12,11,14]. Then you shall reverse
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* the order of the first three (3) elements, and you will get [11,12,13,14]
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*
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* For this assignment you shall implement function
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* that returns list of integers corresponding to the required reversals.
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* E.g. for given vector [12,13,11,14]
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* the function should return [2, 3].
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*/
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std::vector<std::size_t> getReversalsToSort(const std::vector<int> &arr) {
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std::vector<int> intermediate = arr;
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std::vector<std::size_t> ret = {};
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for (std::size_t i = intermediate.size(); i > 1; i--) {
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// only searching the unsorted elements
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auto found =
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std::max_element(intermediate.cbegin(), intermediate.cbegin() + i);
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std::size_t first_swap = found - intermediate.cbegin() + 1;
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std::size_t second_swap = i;
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// remove false positives of elements already being in the correct spot
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if (first_swap != second_swap) {
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// if the element is already the first in the list we don't need to move
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// it there
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if (first_swap > 1) {
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ret.push_back(first_swap);
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std::reverse(intermediate.begin(), intermediate.begin() + first_swap);
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}
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ret.push_back(second_swap);
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std::reverse(intermediate.begin(), intermediate.begin() + second_swap);
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}
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}
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return ret;
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}
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int main(void) {
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std::cout << "{";
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std::vector<int> arr{12, 13, 11, 14};
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for (auto &e : getReversalsToSort(arr)) {
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std::cout << e << ",";
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}
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std::cout << "}\n";
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}
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