golang 算法课 大顶堆模板

func findKthLargest(nums []int, k int) int {
	heapSize := len(nums)
	buildMaxHeap(nums, heapSize)
	for i := len(nums) - 1; i >= len(nums) - k + 1; i-- {
		nums[0], nums[i] = nums[i], nums[0]
		heapSize--
		maxHeapify(nums, 0, heapSize)
	}
	return nums[0]
}

func buildMaxHeap(a []int, heapSize int) {
	for i := heapSize/2; i >= 0; i-- {
		maxHeapify(a, i, heapSize)
	}
}

func maxHeapify(a []int, i, heapSize int) {
	l, r, largest := i * 2 + 1, i * 2 + 2, i
	if l < heapSize && a[l] > a[largest] {
		largest = l
	}
	if r < heapSize && a[r] > a[largest] {
		largest = r
	}
	if largest != i {
		a[i], a[largest] = a[largest], a[i]
		maxHeapify(a, largest, heapSize)
	}
}
// leetcode中的一道题可以当做以后大顶堆的模板， 详见力扣