52 lines
1.4 KiB
C
52 lines
1.4 KiB
C
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/**
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* Sort algorithm for nearly-sorted data.
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*
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* Runtime:
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* - Worst case O(n^2) [smallrange / descending]
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* - random case O(nlogn)
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* Space: same as runtime
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*/
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#include <vector> // can do with malloc only if needed but this spares more ram. Also can do with a stack data type..
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#include <cstdint> // uint32_t
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// TODO: outliersort(...) function with parametrizable "what is an outlier?" and "init" functions!
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// why? Because when I renamed outnsi to outlier I realized the only rule is to keep the begin
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// of the array sorted but otherwise we better put into the outlier data that would make us
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// less likely to be able to fill-in more data points (think of real outliers like [1 9000 2 3 4 ...8999]
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// TODO: simple to make this work with custom comparator and type..
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void nsort(uint32_t *arr, int n) {
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// Temp space - worst case O(n) size
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std::vector<uint32_t> outlier;
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// Split [i: read, j: write]
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uint32_t max = (n > 0) ? arr[0] : 0;
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uint32_t i = 1;
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uint32_t j = 1;
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while(i < n) {
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if(arr[i] < max) {
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outlier.push_back(arr[i++]);
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} else if(i > j) {
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arr[j++] = arr[i++];
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}
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}
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if(outlier.size() > 1) {
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// Recursion
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nsort(&outlier[0], outlier.size());
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// Merge-from-right [j: sorted right-index, i: write index]
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uint32_t k = outlier.size() - 1;
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--j;
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--i;
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while(i >= 0) {
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if(outlier[k] > arr[j]) {
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arr[i--] = outlier[k--];
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} else {
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arr[i--] = arr[j--];
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}
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}
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}
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}
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