40 lines
1.3 KiB
C++
40 lines
1.3 KiB
C++
#include <vector>
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#include <cstdio>
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/**
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* 969. Pancake Sorting
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* Given an array of integers arr, sort the array by performing a series of pancake flips.
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* In one pancake flip we do the following steps:
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* Choose an integer k where 1 <= k <= arr.length.
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* Reverse the sub-array arr[0...k-1] (0-indexed).
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* For example, if arr = [3,2,1,4] and we performed a pancake flip choosing k = 3, we reverse the sub-array [3,2,1], so arr = [1,2,3,4] after the pancake flip at k = 3.
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* Return an array of the k-values corresponding to a sequence of pancake flips that sort arr. Any valid answer that sorts the array within 10 * arr.length flips will be judged as correct.
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*/
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class Solution {
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public:
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static std::vector<int> pancakeSort(std::vector<int>& arr) {
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std::vector<int> ret;
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int n = arr.size();
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ret.reserve(n << 1);
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for (int i = n; i; --i) {
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auto intervalLast = std::next(arr.begin(), i);
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auto maxElement = std::max_element(arr.begin(), intervalLast);
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ret.push_back(1 + std::distance(arr.begin(), maxElement));
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ret.push_back(i);
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std::reverse(arr.begin(), std::next(maxElement));
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std::reverse(arr.begin(), intervalLast);
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}
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return ret;
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}
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};
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int main() {
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std::vector<int> args = {1,2,3};
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auto ret = Solution::pancakeSort(args);
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for (int i : ret) {
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std::printf("%d ", i);
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}
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return 0;
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}
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