[LeetCode] 274. H-Index

轉自LeetCode

Given an array of citations (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 hof 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 = [3,0,6,1,5]
Output: 3 
Explanation: [3,0,6,1,5] means the researcher has 5 papers in total and each of them had 
             received 3, 0, 6, 1, 5 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.

<Solution>

想法如下:

• 將 citation 做分類，分裝到不同的 bucket

• 為什麼選擇用 bucket 的方式分類，因為這邊只在乎在某個數以上的paper數量，和以下的 paper 數量，所以利用 bucket 分類，可以很快計算出以上和以下的數量

• 因為 paper 的數量，剛好等於 array 的長度，所以 bucket 的數量，設為 citations.length + 1，把比 paper 數量多的 citation 都放在同一個 bucket

• 最後，因為題目要求要找最大的 h-index，所以從最後面的 bucket 往前找。當在該 bucket 的數目，已經大於等於該 bucket 的 index時，就找到最大的 h-index 了

code 如下

Java(參考方法)

Kotlin