26 lines
583 B
C++
26 lines
583 B
C++
#include <unordered_set>
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#include <vector>
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/**
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* 128. Longest Consecutive Sequence
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* Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.
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* You must write an algorithm that runs in O(n) time.
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*/
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class Solution {
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public:
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int longestConsecutive(const std::vector<int>& nums) {
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std::unordered_set<int> s(nums.begin(), nums.end());
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int ans = 0;
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for (int i : s) {
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if (s.count(i - 1))
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continue;
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int cur = i, ca = 1;
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for (; s.count(1 + cur); ++cur)
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++ca;
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ans = std::max(ans, ca);
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}
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return ans;
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}
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};
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