题目大意：给你已排序的引用次数的数组，求h-index。
Problem:
https://leetcode.com/problems/h-index-ii/description/
Follow up for H-Index: What if the citations array is sorted in ascending order? Could you optimize your algorithm?
Solution 1: Linear Scan
Time complexity: O(n)
Space complexity: O(1)
C++
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// Author: Huahua // Running time: 33 ms class Solution { public: int hIndex(vector<int>& citations) { for (int i = 1; i <= citations.size(); ++i) if (*(citations.rbegin() + i - 1) < i) return i - 1; return citations.size(); } }; |
Solution 2: Binary Search
Time Complexity: O(logn)
Space Complexity: O(1)
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// Author: Huahua // Running time: 9 ms class Solution { public: int hIndex(vector<int>& citations) { int n = citations.size(); int l = 0; int r = n; while (l < r) { int m = l + (r - l) / 2; if (citations[n - m - 1] <= m) r = m; else l = m + 1; } return l; } }; |
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