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h-index.cpp
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h-index.cpp
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// Time: O(n)
// Space: O(n)
// Counting sort.
class Solution {
public:
int hIndex(vector<int>& citations) {
const auto n = citations.size();
vector<int> count(n + 1, 0);
for (const auto& x : citations) {
// Put all x >= n in the same bucket.
if (x >= n) {
++count[n];
} else {
++count[x];
}
}
int h = 0;
for (int i = n; i >= 0; --i) {
h += count[i];
if (h >= i) {
return i;
}
}
return h;
}
};
// Time: O(nlogn)
// Space: O(1)
class Solution2 {
public:
int hIndex(vector<int>& citations) {
sort(citations.begin(), citations.end(), greater<int>());
int h = 0;
for (const auto& x : citations) {
if (x >= h + 1) {
++h;
} else {
break;
}
}
return h;
}
};