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L128_LongestConsecutiveSequence.cpp
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L128_LongestConsecutiveSequence.cpp
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#pragma warning(disable:4786)
/*
url: leetcode.com/problems/longest-consecutive-sequence
Solution: AC 113ms 0.61%
Solution2: AC 16ms 10.02%
*/
#include <iostream>
#include <set>
#include <vector>
#include <map>
using namespace std;
class Solution {
public :
int _max(int a, int b) {
return a < b ? b : a;
}
int _min(int a, int b) {
return a < b ? a : b;
}
int longestConsecutive(vector<int >& n) {
int nn = n.size(), i = 0;
int max_val = INT_MIN, min_val = INT_MAX;
set<int > s;
for (i = 0; i < nn; i ++) {
max_val = _max(max_val, n[i]);
min_val = _min(min_val, n[i]);
s.insert(n[i]);
}
if (max_val - min_val == nn-1 && s.size() == nn) return nn;
int ans = 0, l = 0, r = 0;
for (i = 0; i < nn; i ++) {
l = n[i];
r = l;
while (s.count(-- l)) {};
while (s.count(++ r)) {};
ans = _max(ans, r - l - 1);
}
return ans;
}
};
class Solution2 {
public :
int _max(int a, int b) {
return a < b ? b : a;
}
int _min(int a, int b) {
return a < b ? a : b;
}
int longestConsecutive(vector<int >& n) {
int ans = 0, i = 0, nn = n.size();
int v = 0, l = 0, r = 0, sum = 0;
map<int, int > m ;
for (i = 0;i < nn; i ++) {
v = n[i];
if (! m.count(v)) {
l = m.count(v-1) ? m[v-1] : 0;
r = m.count(v+1) ? m[v+1] : 0;
sum = l + r + 1;
m[v] = sum;
ans = _max(ans, sum);
m[v-l] = sum;
m[v+r] = sum;
}
}
return ans;
}
};
int main() {
int a[] = {9, 2, 3, 4, 5, 6};
int an = 6;
vector<int > n;
int i = 0;
for (i = 0; i < an; i ++)
n.push_back(a[i]);
cout<<Solution2().longestConsecutive(n)<<endl;
return 0;
}