Leetcode#1985

Find the Kth Largest Integer in the Array

Problem Statement

You are given an array of strings nums and an integer k. Each string in nums represents an integer without leading zeros.

Return the string that represents the kth largest integer in nums.

Note: Duplicate numbers should be counted distinctly. For example, if nums is ["1","2","2"], "2" is the first largest integer, "2" is the second-largest integer, and "1" is the third-largest integer.

Example 1:

Input: nums = ["3","6","7","10"], k = 4
Output: "3"
Explanation:
The numbers in nums sorted in non-decreasing order are ["3","6","7","10"].
The 4th largest integer in nums is "3".

Example 2:

Input: nums = ["2","21","12","1"], k = 3
Output: "2"
Explanation:
The numbers in nums sorted in non-decreasing order are ["1","2","12","21"].
The 3rd largest integer in nums is "2".

Example 3:

Input: nums = ["0","0"], k = 2
Output: "0"
Explanation:
The numbers in nums sorted in non-decreasing order are ["0","0"].
The 2nd largest integer in nums is "0".

Constraints:

• 1 <= k <= nums.length <= 104
• 1 <= nums[i].length <= 100
• nums[i] consists of only digits.
• nums[i] will not have any leading zeros.

Golang solution

type Minheap []string

func (h Minheap) Len() int {
	return len(h)
}
func (h Minheap) Less(i, j int) bool {

	// check if lengths are same
	if len(h[i]) == len(h[j]) {
		return h[i] < h[j]
	}

	// return based on lexographical order
	return len(h[i]) < len(h[j])
}

func (h Minheap) Swap(i, j int) {
	h[i], h[j] = h[j], h[i]
}

func (h *Minheap) Push(item interface{}) {
	*h = append(*h, item.(string))
}

func (h *Minheap) Pop() interface{} {
	length := len(*h)
	item := (*h)[length-1]
	(*h) = (*h)[0 : length-1]
	return item
}

func kthLargestNumber(nums []string, k int) string {
	h := &Minheap{}
	heap.Init(h)

	for _, val := range nums {
		// v, _ := strconv.ParseUint(val, 10, 64)
		// heap.Push(h, v)
		heap.Push(h, val)

		// keep total items in heap at most k
		if h.Len() > k {
			heap.Pop(h)
		}
	}

	// result := []string{}
	// for h.Len() > 0 {
	//     item := heap.Pop(h)
	//     result = append(result, item.(string))
	// }

	ans := heap.Pop(h).(string)
	return ans
}

Output

Input
nums = ["3","6","7","10"]
k = 4

Output
"3"

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