Given an unsorted array of integers, find the length of the longest consecutive elements sequence.
For example,Given [100, 4, 200, 1, 3, 2],The longest consecutive elements sequence is [1, 2, 3, 4].
Return its length: 4.
Your algorithm should run in O(n) complexity.
class Solution {
public:
int longestConsecutive(vector<int>& nums) {
if(nums.size()<=0)
return 0;
unordered_set<int> exsitSet;
unordered_set<int> visitedSet;
for(int i=0;i<nums.size();i++)
exsitSet.insert(nums[i]);
int maxLen = 0;
for(int i=0;i<nums.size();i++)
{
if(visitedSet.find(nums[i]) != visitedSet.end())
continue;
int count = 1;
int left = nums[i];
while(exsitSet.find(--left) != exsitSet.end())
{
count++;
visitedSet.insert(left);
}
int right = nums[i];
while(exsitSet.find(++right) != exsitSet.end())
{
count++;
visitedSet.insert(right);
}
maxLen = max(maxLen,count);
}
return maxLen;
}
};
