Add h index (TheAlgorithms#8036)

Author: alexpantyukhin

Diff for: DIRECTORY.md

@@ -712,6 +712,7 @@
   * [Gauss Easter](other/gauss_easter.py)
   * [Graham Scan](other/graham_scan.py)
   * [Greedy](other/greedy.py)
+  * [H Index](other/h_index.py)
   * [Least Recently Used](other/least_recently_used.py)
   * [Lfu Cache](other/lfu_cache.py)
   * [Linear Congruential Generator](other/linear_congruential_generator.py)

Diff for: other/h_index.py

@@ -0,0 +1,71 @@
+"""
+Task:
+Given an array of integers citations where citations[i] is the number of
+citations a researcher received for their ith paper, return compute the
+researcher's h-index.
+
+According to the definition of h-index on Wikipedia: A scientist has an
+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.
+
+If there are several possible values for h, the maximum one is taken as the
+h-index.
+
+H-Index link: https://en.wikipedia.org/wiki/H-index
+
+Implementation notes:
+Use sorting of array
+
+Leetcode link: https://leetcode.com/problems/h-index/description/
+
+n = len(citations)
+Runtime Complexity: O(n * log(n))
+Space  Complexity: O(1)
+
+"""
+
+
+def h_index(citations: list[int]) -> int:
+    """
+    Return H-index of citations
+
+    >>> h_index([3, 0, 6, 1, 5])
+    3
+    >>> h_index([1, 3, 1])
+    1
+    >>> h_index([1, 2, 3])
+    2
+    >>> h_index('test')
+    Traceback (most recent call last):
+        ...
+    ValueError: The citations should be a list of non negative integers.
+    >>> h_index([1,2,'3'])
+    Traceback (most recent call last):
+        ...
+    ValueError: The citations should be a list of non negative integers.
+    >>> h_index([1,2,-3])
+    Traceback (most recent call last):
+        ...
+    ValueError: The citations should be a list of non negative integers.
+    """
+
+    # validate:
+    if not isinstance(citations, list) or not all(
+        isinstance(item, int) and item >= 0 for item in citations
+    ):
+        raise ValueError("The citations should be a list of non negative integers.")
+
+    citations.sort()
+    len_citations = len(citations)
+
+    for i in range(len_citations):
+        if citations[len_citations - 1 - i] <= i:
+            return i
+
+    return len_citations
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()