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DSUの改善 #22

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Merged
NASU41 merged 3 commits into from
Sep 9, 2020
Merged

DSUの改善 #22

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16c5456
format
falrnd Sep 9, 2020
7b35ac2
exception
falrnd Sep 9, 2020
a95a345
groups
falrnd Sep 9, 2020
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141 changes: 72 additions & 69 deletions DSU/DSU.java
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Original file line number Diff line number Diff line change
@@ -1,70 +1,73 @@
class DSU{
private int n;
private int[] parentOrSize;

public DSU(int n){
this.n = n;
this.parentOrSize = new int[n];
Arrays.fill(parentOrSize,-1);
}

int merge(int a, int b){
if(!(0 <= a && a < n) || !(0 <= b && b < n)){
// この式が成立しない物は動作しません。
return -1;
}
int x = leader(a);
int y = leader(b);
if(x == y) return x;
if(-parentOrSize[x] < -parentOrSize[y]){
int tmp = x;
x = y;
y = tmp;
}
parentOrSize[x] += parentOrSize[y];
parentOrSize[y] = x;
return x;
}

boolean same(int a, int b){
if(!(0 <= a && a < n) || !(0 <= b && b < n)){
// この式が成立しない物は動作しません。
return false;
}
return leader(a) == leader(b);
}

int leader(int a){
if (parentOrSize[a] < 0){
return a;
}else{
parentOrSize[a] = leader(parentOrSize[a]);
return parentOrSize[a];
}
}
import java.util.ArrayList;
import java.util.Arrays;

int size(int a) {
if(!(0 <= a && a < n)){
// この式が成立しない物は動作しません。
return -1;
}
return -parentOrSize[leader(a)];
}

ArrayList<ArrayList<Integer>> groups(){
int[] leaderBuf = new int[n];
int[] groupSize = new int[n];
for(int i = 0; i < n; i++){
leaderBuf[i] = leader(i);
groupSize[leaderBuf[i]]++;
}
ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
for(int i = 0; i < n; i++){
result.add(new ArrayList<>());
}
for(int i = 0; i < n; i++){
result.get(leaderBuf[i]).add(i);
}
return result;
}
}
class DSU {
private int n;
private int[] parentOrSize;

public DSU(int n) {
this.n = n;
this.parentOrSize = new int[n];
Arrays.fill(parentOrSize, -1);
}

int merge(int a, int b) {
if (!(0 <= a && a < n))
throw new IndexOutOfBoundsException("a=" + a);
if (!(0 <= b && b < n))
throw new IndexOutOfBoundsException("b=" + b);

int x = leader(a);
int y = leader(b);
if (x == y) return x;
if (-parentOrSize[x] < -parentOrSize[y]) {
int tmp = x;
x = y;
y = tmp;
}
parentOrSize[x] += parentOrSize[y];
parentOrSize[y] = x;
return x;
}

boolean same(int a, int b) {
if (!(0 <= a && a < n))
throw new IndexOutOfBoundsException("a=" + a);
if (!(0 <= b && b < n))
throw new IndexOutOfBoundsException("b=" + b);
return leader(a) == leader(b);
}

int leader(int a) {
if (parentOrSize[a] < 0) {
return a;
} else {
parentOrSize[a] = leader(parentOrSize[a]);
return parentOrSize[a];
}
}

int size(int a) {
if (!(0 <= a && a < n))
throw new IndexOutOfBoundsException("" + a);
return -parentOrSize[leader(a)];
}

ArrayList<ArrayList<Integer>> groups() {
int[] leaderBuf = new int[n];
int[] groupSize = new int[n];
for (int i = 0; i < n; i++) {
leaderBuf[i] = leader(i);
groupSize[leaderBuf[i]]++;
}
ArrayList<ArrayList<Integer>> result = new ArrayList<>(n);
for (int i = 0; i < n; i++) {
result.add(new ArrayList<>(groupSize[i]));
}
for (int i = 0; i < n; i++) {
result.get(leaderBuf[i]).add(i);
}
result.removeIf(ArrayList::isEmpty);
return result;
}
}