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#include <iostream>
#include <vector>
#include <algorithm>
//#include <gtest/gtest.h>
using std::vector;
using std::cin;
using std::cout;
using std::swap;
using std::pair;
using std::make_pair;
class HeapBuilder {
private:
vector<int> data_;
// vector<pair<int, int> > swaps_;
// void GenerateSwaps() {
// swaps_.clear();
// // The following naive implementation just sorts
// // the given sequence using selection sort algorithm
// // and saves the resulting sequence of swaps.
// // This turns the given array into a heap,
// // but in the worst case gives a quadratic number of swaps.
// //
// for (size_t i = 0; i < data_.size(); ++i)
// for (size_t j = i + 1; j < data_.size(); ++j) {
// if (data_[i] > data_[j]) {
// swap(data_[i], data_[j]);
// swaps_.push_back(make_pair(i, j));
// }
// }
// }
public:
vector<pair<int, int>> swaps;
void WriteResponse() const {
cout << swaps.size() << "\n";
for (size_t i = 0; i < swaps.size(); ++i) {
cout << swaps[i].first << " " << swaps[i].second << "\n";
}
}
void ReadData() {
int n;
cin >> n;
data_.resize(n);
for (int i = 0; i < n; ++i)
cin >> data_[i];
}
// Please note the for loop below. Initially I copied the for loop from my
// Java code, but it doesn't work in C++. Changing it to while loop worked!
// It was better with the while loop anyway, much clearer to me.
void UpdateSwaps(vector<int> &data) {
int j = (data.size() - 1) / 2;
while (j >= 0) {
siftDown(j, data);
j = j - 1;
}
// for (size_t i = j; i >= 0; i--) {
// siftDown(i, data);
// }
}
void siftDown(int i, vector<int> &data) {
int maxIndex = i;
size_t l = 2 * i + 1;
if (l < data.size() && data[l] < data[maxIndex])
maxIndex = l;
size_t r = 2 * i + 2;
if (r < data.size() && data[r] < data[maxIndex])
maxIndex = r;
if (i != maxIndex) {
swap(data[i], data[maxIndex]);
swaps.push_back(make_pair(i, maxIndex));
siftDown(maxIndex, data);
}
}
void Solve() {
ReadData();
// GenerateSwaps();
UpdateSwaps(data_);
WriteResponse();
}
};
int main() {
// vector<int> data = { 5, 4, 3, 2, 1 };
// HeapBuilder heap_builder;
// heap_builder.UpdateSwaps(data);
// heap_builder.WriteResponse();
std::ios_base::sync_with_stdio(false);
HeapBuilder heap_builder;
heap_builder.Solve();
return 0;
}
//TEST(BuildHeap, t) {
// vector<int> data = {5, 4, 3, 2, 1};
// HeapBuilder heap_builder;
// heap_builder.UpdateSwaps(data);
// ASSERT_EQ(3, heap_builder.swaps.size());
// ASSERT_EQ(1, heap_builder.swaps[0].first);
// ASSERT_EQ(4, heap_builder.swaps[0].second);
// ASSERT_EQ(0, heap_builder.swaps[1].first);
// ASSERT_EQ(1, heap_builder.swaps[1].second);
// ASSERT_EQ(1, heap_builder.swaps[2].first);
// ASSERT_EQ(3, heap_builder.swaps[2].second);
//}
//
//TEST(BuildHeap, t1) {
// vector<int> data = {1, 2, 3, 4, 5};
// HeapBuilder heap_builder;
// heap_builder.UpdateSwaps(data);
// ASSERT_EQ(0, heap_builder.swaps.size());
//}
//
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