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package leetcode.hard;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
public class P_128 {
private static final class UnionFind {
private final int[] parent;
private final int[] size;
private int count;
private UnionFind(int n) {
parent = new int[n];
size = new int[n];
count = n;
for (int i = 0; i < n; i++) {
parent[i] = i;
size[i] = 1;
}
}
public int find(int p) {
// path compression
while (p != parent[p]) {
parent[p] = parent[parent[p]];
p = parent[p];
}
return p;
}
public void union(int p, int q) {
final int rootP = find(p);
final int rootQ = find(q);
if (rootP == rootQ) {
return;
}
// union by size
if (size[rootP] > size[rootQ]) {
parent[rootQ] = rootP;
size[rootP] += size[rootQ];
} else {
parent[rootP] = rootQ;
size[rootQ] += size[rootP];
}
count--;
}
public int count() { return count; }
public int[] size() { return size; }
}
public int longestConsecutiveMap(int[] nums) {
final Map<Integer, Integer> index = new HashMap<>();
final int n = nums.length;
for (int i = 0; i < n; i++) {
index.put(nums[i], i);
}
final UnionFind uf = new UnionFind(n);
for (int num : nums) {
final Integer l = index.get(num - 1);
final Integer curr = index.get(num);
final Integer r = index.get(num + 1);
if (l != null) {
uf.union(l, curr);
}
if (r != null) {
uf.union(r, curr);
}
}
int res = 0;
for (int i = 0; i < n; i++) {
res = Math.max(res, uf.size[i]);
}
return res;
}
public int longestConsecutive(int[] nums) {
final int n = nums.length;
final UnionFind uf = new UnionFind(n);
Arrays.sort(nums);
for (int i = 0; i < n; i++) {
if (i > 0 && nums[i - 1] == nums[i]) {
continue;
}
final int l = lowerBound(nums, nums[i] - 1);
final int r = lowerBound(nums, nums[i] + 1);
if (l != n && nums[l] == nums[i] - 1) {
uf.union(l, i);
}
if (r != n && nums[r] == nums[i] + 1) {
uf.union(r, i);
}
}
int res = 0;
for (int i = 0; i < n; i++) {
res = Math.max(res, uf.size[i]);
}
return res;
}
private static int lowerBound(int[] arr, int target) {
int lo = 0, hi = arr.length;
while (lo < hi) {
final int mid = lo + hi >>> 1;
if (arr[mid] < target) {
lo = mid + 1;
} else {
hi = mid;
}
}
return lo;
}
}