Heap (maxheap) implementation
A simple, rough and ready, maxheap implementation. It uses an vector as an implicit complete binary tree:
#include <iostream>
#include <stdlib.h>
#include <vector>
#include <algorithm>
#include <limits.h>
using namespace std;
class Heap {
public:
Heap() {
store.push_back(0);
}
int l_child(int idx) {
return idx*2;
}
int r_child(int idx) {
return (idx*2)+1;
}
int get_parent(int idx) {
return (idx/2);
}
void insert(int val) {
store.push_back(val);
int idx = store.size()-1;
if(idx == 1) return;
// bubble up
for(;store[get_parent(idx)] < store[idx];) {
int t = store[get_parent(idx)];
store[get_parent(idx)] = val;
store[idx] = t;
idx = get_parent(idx);
if(get_parent(idx) == 0) break;
}
}
void dump() {
cout << "DUMPSTART" << endl;
for(size_t n=0;n<store.size();n++) {
cout << store[n] << endl;
}
cout << "DUMPEND" << endl;
}
int pop() {
int r = store[1];
store[1] = store[store.size()-1];
store.pop_back();
bool min=true;
int idx = 1;
for(;min==true;) {
min=false;
int lidx = l_child(idx);
int ridx = r_child(idx);
int lval;
int rval;
if(lidx < store.size()) lval = store[lidx]; else lval = INT_MIN;
if(ridx < store.size()) rval = store[ridx]; else rval = INT_MIN;
if(store[idx] < lval) { min=true; }
if(store[idx] < rval) { min=true; }
if(!min) break;
int t = store[idx];
if(lval > rval) {
store[idx] = store[l_child(idx)];
store[l_child(idx)] = t;
idx = l_child(idx);
} else {
store[idx] = store[r_child(idx)];
store[r_child(idx)] = t;
idx = r_child(idx);
}
}
return r;
}
vector<int> store;
};
int main() {
vector<int> testdata;
for(size_t n=0;n<10;n++) testdata.push_back(rand()%20);
Heap myheap;
for(size_t n=0;n<testdata.size();n++) myheap.insert(testdata[n]);
cout << "popping heap:" << endl;
for(size_t n=0;n<testdata.size();n++) cout << myheap.pop() << endl;
cout << "sorted testdata:" << endl;
sort(testdata.rbegin(),testdata.rend());
for(size_t n=0;n<testdata.size();n++) cout << testdata[n] << endl;
cout << "second test: " << endl;
Heap myheap2;
for(size_t n=0;n<testdata.size();n++) myheap2.insert(testdata[n]);
for(size_t n=0;n<(testdata.size()/2);n++) cout << myheap2.pop() << endl;
myheap2.insert(100);
myheap2.insert(7);
for(size_t n=0;n<(testdata.size()/2)+2;n++) cout << myheap2.pop() << endl;
}
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