274 H-Index

Given an array of integers citations where citations[i] is the number of citations a researcher received for their i-th paper, compute the researcher's h-index.

The h-index is defined as: A scientist has index h if h of their n papers have at least h citations each, and the other n − h papers have no more than h citations each.

Example 1:

Input: citations = [3,0,6,1,5]
Output: 3
Explanation: The researcher has 5 papers in total.
3 of them have at least 3 citations each and the remaining 2 have no more than 3 citations each.

Example 2:

Input: citations = [1,3,1]
Output: 1

Constraints:

• n == citations.length
• 1 <= n <= 5000
• 0 <= citations[i] <= 1000

Approach (Sorting / Greedy)

1. Sort citations.
2. Iterate through the sorted array from large to small number. For each paper at index i, check if citation is large or equal to count.

Time Complexity: O(n log n)
Space Complexity: O(1) if in-place sorting.

Solution:

Javascript Solution

var hIndex = function(citations) {
    citations.sort((a, b) => b - a)
    let h = 0
    for(let i = 0; i < citations.length; i++) {
        if(citations[i] >= i + 1) {
            h = i + 1
        } else {
            break
        }
    }
    return h
};

TypeScript Solution

function hIndex(citations: number[]): number {
    citations.sort((a, b) => b - a)
    let h = 0
    for(let i = 0; i < citations.length; i++) {
        if(citations[i] >= i + 1) {
            h = i + 1
        } else {
            break
        }
    }
    return h
};