Created
March 30, 2019 13:37
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Quick Sort (iterative)
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#include <iostream> | |
#include <vector> | |
#include <stack> | |
template <class T> | |
int partition(std::vector<T>& vals, int l, int r) { | |
int i=l-1, j=r, v=vals[r]; | |
for (;;) { | |
while (vals[++i] < v) ; | |
while (vals[--j] > v) if (j<1) break; | |
if (i>=j) break; | |
std::swap(vals[i], vals[j]); | |
} | |
std::swap(vals[i], vals[r]); | |
return i; | |
} | |
template <class T> | |
void quicksort(std::vector<T>& vals, int l, int r) { | |
std::stack<std::pair<int,int>> s; | |
s.push({l,r}); | |
while (s.size() > 0) { | |
auto bounds = s.top(); | |
s.pop(); | |
int cur_l = bounds.first; | |
int cur_r = bounds.second; | |
if (cur_r-cur_l >= 1) { | |
int i = partition(vals, cur_l, cur_r); | |
s.push({cur_l,i-1}); | |
s.push({i+1,cur_r}); | |
} | |
} | |
} | |
template <class T> | |
void quicksort(std::vector<T>& vals) { | |
quicksort(vals, 0, vals.size()-1); | |
} | |
template <class T> | |
void print_v(const std::vector<T>& vals) { | |
for (auto val : vals) | |
std::cout << val << " "; | |
std::cout << std::endl; | |
} | |
int main() | |
{ | |
std::vector<int> nums { 5,2,8,1,4,3,7,6 }; | |
print_v(nums); | |
quicksort(nums); | |
print_v(nums); | |
return 0; | |
} |
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