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839.java
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839.java
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__________________________________________________________________________________________________
sample 104 ms submission
class Solution {
public int numSimilarGroups(String[] A) {
int N = A.length;
int M = A[0].length();
if (N > M * M) {
return generationMethod(A);
} else {
return comparationMethod(A);
}
}
// O(N * M * (M - 1) / 2 * M)
// O(N ^ 2 * M ^ 3)
private int generationMethod(String[] A) {
Map<String, Integer> map = new HashMap<>();
for (int i = 0; i < A.length; i++) {
map.putIfAbsent(A[i], i);
}
UF uf = new UF();
for (int i : map.values()) {
uf.add(i);
}
// N words
for (Map.Entry<String, Integer> e : map.entrySet()) {
char[] s = e.getKey().toCharArray();
int i = e.getValue();
// M * (M - 1) / 2 swaps
for (int j = 0; j < s.length; j++) {
for (int k = j + 1; k < s.length; k++) {
swap(s, j, k);
// build string take O(M)
// iteration take O(N) in total
Integer t = map.get(new String(s));
if (t != null) {
uf.union(i, t);
}
swap(s, j, k);
}
}
}
return uf.count;
}
// O(N ^ 2 * M)
private int comparationMethod(String[] A) {
Set<String> set = new HashSet<>();
for (String s : A) {
set.add(s);
}
A = set.toArray(new String[0]);
UF uf = new UF();
for (int i = 0; i < A.length; i++) {
uf.add(i);
}
for (int i = 0; i < A.length; i++) {
for (int j = i + 1; j < A.length; j++) {
if (isSimilar(A[i], A[j])) {
uf.union(i, j);
}
}
}
return uf.count;
}
private void swap(char[] arr, int i, int j) {
char c = arr[i];
arr[i] = arr[j];
arr[j] = c;
}
private boolean isSimilar(String a, String b) {
int diffCnt = 0;
for (int i = 0; i < a.length(); i++) {
if (a.charAt(i) != b.charAt(i)) {
diffCnt++;
}
if (diffCnt > 2) {
return false;
}
}
return diffCnt <= 2;
}
private class UF {
private Map<Integer, UFNode> map;
private int count;
private UF() {
map = new HashMap<>();
}
private void add(int val) {
if (!map.containsKey(val)) {
map.put(val, new UFNode());
count++;
}
}
private UFNode find(int val) {
return find(map.get(val));
}
private UFNode find(UFNode n) {
if (n.parent != n) {
n.parent = find(n.parent);
}
return n.parent;
}
private void union(int a, int b) {
UFNode rootA = find(a);
UFNode rootB = find(b);
if (rootA == rootB) {
return;
}
if (rootA.rank < rootB.rank) {
rootA.parent = rootB;
} else {
rootB.parent = rootA;
if (rootA.rank == rootB.rank) {
rootA.rank++;
}
}
count--;
}
private class UFNode {
private UFNode parent = this;
private int rank = 0;
}
}
}
__________________________________________________________________________________________________
sample 38288 kb submission
class Solution {
public int numSimilarGroups(String[] a) {
int n = a.length;
int[] parent = new int[n];
for (int i = 1; i < n; i++) parent[i] = i;
for (int i = 0; i < n - 1; i++) {
for (int j = i + 1; j < n; j++) {
if (isSimilarString(a[i], a[j])) {
int p1 = find(parent, i), p2 = find(parent, j);
if (p1 != p2) {
parent[p2] = p1;
}
}
}
}
int res = 0;
for (int i = 0; i < n; i++) {
if (parent[i] == i) res++;
}
return res;
}
private boolean isSimilarString(String s1, String s2) {
int diff = 0;
for (int i = 0; i < s1.length(); i++) {
if (s1.charAt(i) != s2.charAt(i)) diff++;
}
return (diff == 2 || diff == 0);
}
private int find(int[] a, int x) {
if (a[x] != x) {
a[x] = find(a, a[x]);
}
return a[x];
}
}
__________________________________________________________________________________________________