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.
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public
class
Solution {
public
int
longestConsecutive(int[] num) {
int
length = 0;
if(num.length > 0){
length = 1;
Map<Integer, Integer> lens = new
HashMap<Integer, Integer>();
Map<Integer, Integer> visited = new
HashMap<Integer, Integer>();
for(int
i = 0; i < num.length; ++i){
lens.put(num[i], 1);
visited.put(num[i], 0);
}
for(int
i = 0; i < num.length; ++i){
if(visited.get(num[i]) != 0)
continue;
else{
visited.put(num[i], 1);
if(lens.containsKey(num[i] - 1)){
if(visited.get(num[i] - 1) == 0){
int
templength = lens.get(num[i] - 1) + lens.get(num[i]);
lens.put(num[i], templength);
lens.put(num[i] - lens.get(num[i] - 1), templength);
length = (length < templength)? templength: length;
visited.put(num[i] - 1, 1);
}
}
if(lens.containsKey(num[i] + 1)){
int
templength = lens.get(num[i] + 1) + lens.get(num[i]);
lens.put(num[i] - lens.get(num[i]) + 1, templength);
lens.put(num[i] + lens.get(num[i] + 1), templength);
length = (length < templength)? templength: length;
}
}
}
}
return
length;
}
} |