LeetCode: H-Index II

H-Index II

Similar Problems:

• LeetCode: H-Index
• CheatSheet: Leetcode For Code Interview
• CheatSheet: Common Code Problems & Follow-ups
• Tag: #array, #binarysearch

Given an array of citations sorted in ascending order (each citation is a non-negative integer) of a researcher, write a function to compute the researcher’s h-index.

According to the definition of h-index on Wikipedia: “A scientist has index h if h of his/her N papers have at least h citations each, and the other N – h papers have no more than h citations each.”

Example:

Input: citations = [0,1,3,5,6]
Output: 3 
Explanation: [0,1,3,5,6] means the researcher has 5 papers in total and each of them had 
             received 0, 1, 3, 5, 6 citations respectively. 
             Since the researcher has 3 papers with at least 3 citations each and the remaining 
             two with no more than 3 citations each, her h-index is 3.

Note:

If there are several possible values for h, the maximum one is taken as the h-index.

Follow up:

• This is a follow up problem to H-Index, where citations is now guaranteed to be sorted in ascending order.
• Could you solve it in logarithmic time complexity?

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

• Solution: array

// https://code.dennyzhang.com/h-index-ii
// Basic Ideas: array
//
// Complexity: Time O(n), Space O(1)
func hIndex(citations []int) int {
    res := 0
    i:=len(citations)-1
    for ; i>=0 && citations[i] >= (res+1); i-- {
        res++
    }
    return res
}