C++实现_topk排序

一、topk_堆排

#include<iostream>
#include<vector>
#include<algorithm>
//堆排序
using namespace std;
void Swap(vector<int>& tree, int a, int b) {
	int temp = tree[a];
	tree[a] = tree[b];
	tree[b] = temp;
}
void heapify(vector<int>& tree, int n, int i) {
	if (i >= n)
		return;
	int min = i;
	int c1 = 2 * i + 1;
	int c2 = 2 * i + 2;
	if (c1<n && tree[c1] < tree[min]) {
		min = c1;
	}
	if (c2<n && tree[c2] < tree[min]) {
		min = c2;
	}
	if (min != i) {
		Swap(tree, min, i);
		heapify(tree, n, min);
	}
}
void print(vector<int>& tree,int n) {
	for (int i = 0; i < n; i++) {
		printf("%d ", tree[i]);
	}
	printf("\n");
}
void build_heap(vector<int>& tree,int n) {
	int last_node = n - 1;
	int parent = (last_node - 1) / 2;
	for (int i = parent; i >= 0; i--) {
		heapify(tree, n, i);
	}
}

//核心
void heap_sort(vector<int>&arr,vector<int>&tree,int n) {
	for (int i = n+1; i < arr.size();i++) {
		build_heap(tree, n);
		print(tree, n);
		if (arr[i] > tree[0]) {
			tree[0] = arr[i];
		}
	}
}

int main() {
	vector<int> tree = { 2,3,4,15,2,15,534,34,53,4645,6,1234,23423,23423,2,6354,62,54123,4,12 };
	/*验证
	sort(tree.begin(), tree.end());
	print(tree, tree.size());*/
	vector<int> arr = tree;
	int n = 7;
	heap_sort(arr,tree, n);
	return 0;
}

 二、topk_sort排序

#include <iostream>
#include <vector>
#include <algorithm>

template <typename T>
void sorts(std::vector<T>& v) {
	// sort vector ----- Ascend
	 sort(v.begin(), v.end());
}

template <typename T>
void print(std::vector<T>& v) {
	for (auto num : v)
		std::cout << num << " ";
	std::cout << std::endl;
}

template <typename T>
std::vector<T> topK(std::vector<T>& v, int k) {
	std::vector<T> tmp(v.begin(), v.begin() + k);

	for (int i = k + 1; i < v.size(); ++i) {
		sorts(tmp);
		print(tmp);
		if (v[i] < tmp[0])
			continue;
		tmp[0] = v[i];
	}
	return tmp;
}

int main() {
	std::vector<int> v = { 2,3,4,15,2,15,534,34,53,4645,6,1234,23423,23423,2,6354,62,54123,4,12 };
	std::vector<int> res = topK(v, 7);
	print(res);

	return 0;
}

本文地址：https://blog.csdn.net/SmartDemo/article/details/107572238