h-index

class Solution {
    public int hIndex(int[] citations) {
        var len = citations.length;
        if (len == 1){
            if (citations[0] == 0){
                return 0;
            } else {
                return 1;
            }
        }
        sort(citations,0 ,(len-1));
        //displayArray(citations);
        var cur = len -1;
        while(cur > 0 && citations[cur] < cur){
            cur--;
        }
        var ret = citations[cur] > (cur+1) ? (cur+1) : citations[cur];
        return ret;
    }

    //The below code is separate from the problem and is used to sort the given integer array.
    //Quick sort is used with mid element as the pivot to sort in decending order.
    private void sort(int[] ar, int l, int h){
        if (l < h){
            var pivot = partision(ar, l, h);
            sort(ar, l, (pivot - 1));
            sort(ar, (pivot + 1), h);
        }
    }

    private int partision(int[] ar, int l, int h){
        int m = (l+h) / 2;
        var pivot = ar[m];
        var marker = (l-1);
        for(int cur = l; cur <= h; cur++){
            if(ar[cur] > pivot){
                marker++;
                swap(ar, marker, cur);
                if (marker == m){
                    m = cur;
                }
            }
        }
        swap(ar, (marker+1), m);
        return (marker+1);
    }

    private void swap(int[] ar, int a, int b){
        var tmp = ar[a];
        ar[a] = ar[b];
        ar[b] = tmp;
    }

}

Leet Code

Given an integer array where the ith index has the count of citations on the ith paper of an author, we need to get the H-index.

Achievement

• The above code beats 66% of the total solutions submitted in terms of runtime with the runtime as 1ms and beats 35% of total solutions submitted in terms of space complexity.
• I have implemented quick sort learned previously with pivot as a middle index.

H-Index

The h-index is a metric to rate an author's success based on the count of citations on the papers published by him/her.
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