H-Index - Google Top Interview Questions

Problem Statement :

In academia, the h-index is a metric used to calculate the impact of a researcher's papers. It is calculated as follows:

A researcher has index h if at least h papers have at least h citations each. If there are multiple h satisfying this formula, the maximum is chosen.

Given a list of paper citations of a researcher citations, calculate their h-index.


n ≤ 100,000 where n is the length of citations
Example 1
citations = [4, 3, 0, 1, 5]
At least 3 papers have at least 3 citations each: 3, 4, 5.

Example 2
citations = [4, 4, 0, 1, 5, 9]
At least 4 papers have 4 citations each: 4, 4, 5, 9.

Example 3


citations = [9, 10, 0, 1, 6]




At least 3 papers have 3 citations each: 6, 9, 10.

Solution :


                        Solution in C++ :

int solve(vector<int>& citations) {
    int h = 0, N = citations.size();
    sort(citations.begin(), citations.end());
    for (int i = 0; i < N; i++) {
        if (citations[i] >= h && N - i >= h) {
            h = min(citations[i], N - i);
    return h;

                        Solution in Java :

import java.util.*;

class Solution {
    public int solve(int[] citations) {
        int n = citations.length;
        int hIndex = Integer.MIN_VALUE;
        for (int i = 0; i < n; i++) {
            int hPapers = n - i;
            int hCitations = citations[i];
            hIndex = Math.max(hIndex, Math.min(hPapers, hCitations));
        return hIndex;

                        Solution in Python : 
class Solution:
    def solve(self, citations):
        lo, hi = 0, len(citations)
        while lo < hi:
            mid = (lo + hi + 1) // 2
            cnt = 0
            for citation in citations:
                if citation >= mid:
                    cnt += 1
            if cnt >= mid:
                lo = mid
                hi = mid - 1
        return lo

View More Similar Problems

Largest Rectangle

Skyline Real Estate Developers is planning to demolish a number of old, unoccupied buildings and construct a shopping mall in their place. Your task is to find the largest solid area in which the mall can be constructed. There are a number of buildings in a certain two-dimensional landscape. Each building has a height, given by . If you join adjacent buildings, they will form a solid rectangle

View Solution →

Simple Text Editor

In this challenge, you must implement a simple text editor. Initially, your editor contains an empty string, S. You must perform Q operations of the following 4 types: 1. append(W) - Append W string to the end of S. 2 . delete( k ) - Delete the last k characters of S. 3 .print( k ) - Print the kth character of S. 4 . undo( ) - Undo the last (not previously undone) operation of type 1 or 2,

View Solution →

Poisonous Plants

There are a number of plants in a garden. Each of the plants has been treated with some amount of pesticide. After each day, if any plant has more pesticide than the plant on its left, being weaker than the left one, it dies. You are given the initial values of the pesticide in each of the plants. Determine the number of days after which no plant dies, i.e. the time after which there is no plan

View Solution →

AND xor OR

Given an array of distinct elements. Let and be the smallest and the next smallest element in the interval where . . where , are the bitwise operators , and respectively. Your task is to find the maximum possible value of . Input Format First line contains integer N. Second line contains N integers, representing elements of the array A[] . Output Format Print the value

View Solution →


You are a waiter at a party. There is a pile of numbered plates. Create an empty answers array. At each iteration, i, remove each plate from the top of the stack in order. Determine if the number on the plate is evenly divisible ith the prime number. If it is, stack it in pile Bi. Otherwise, stack it in stack Ai. Store the values Bi in from top to bottom in answers. In the next iteration, do the

View Solution →

Queue using Two Stacks

A queue is an abstract data type that maintains the order in which elements were added to it, allowing the oldest elements to be removed from the front and new elements to be added to the rear. This is called a First-In-First-Out (FIFO) data structure because the first element added to the queue (i.e., the one that has been waiting the longest) is always the first one to be removed. A basic que

View Solution →