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LeetCode: 275. H-Index II

木樨点点 2022-12-05 阅读 22


LeetCode: 275. H-Index II

题目描述

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

Follow up:

  • This is a follow up problem to H-Index, where citations is now guaranteed to be sorted in ascending order.
    Could you solve it in logarithmic time complexity?

解题思路 —— 二分查找

  • ​citations[mid] >= citations.size()-mid​​​: 尝试在 ‘[left, mid)’ 寻找使得 ​​h​​​ 更大的 ​​mid​
  • 否则, 尝试在 ‘[mid, right)’ 寻找符合题意的 ​​mid​

AC 代码

class Solution 
{
public:
int hIndex(vector<int>& citations)
{
int left = 0, right = citations.size();
while(left < right)
{
int mid = (left+right)/2;
if(citations[mid] >= citations.size()-mid)
{
// [left, mid)
right = mid;
}
else
{
// [mid+1, right)
left = mid + 1;
}
}

return citations.size()-left;
}
};


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