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-rw-r--r--datastructures/unionFind2.cpp33
1 files changed, 17 insertions, 16 deletions
diff --git a/datastructures/unionFind2.cpp b/datastructures/unionFind2.cpp
index 5362c4d..d1b9162 100644
--- a/datastructures/unionFind2.cpp
+++ b/datastructures/unionFind2.cpp
@@ -1,25 +1,26 @@
-vector<int> uf;
+// unions[i] >= 0 => unions[i] = parent
+// unions[i] < 0 => unions[i] = -size
+vector<int> unions;
-init(int N) {
- uf.assign(N,-1); //-1 indicates that every subset has size 1
+init(int n) {
+ unions.assign(n, -1);
}
int findSet(int i) {
- if(uf[i] < 0) return i; //If uf[i] < 0 we have reach a root
- uf[i] = findSet(uf[i]); //Path-Compression
- return uf[i];
+ if (unions[i] < 0) return i;
+ return unions[i] = findSet(unions[i]);
}
-void linkSets(int i, int j) {
- //Take |uf[i]|, where i must be a root, to get the size
- //of the subset
- if(abs(uf[i]) < abs(uf[j])) { //Union-by-size.
- uf[j] += uf[i]; uf[i] = j;
- } else {
- uf[i] += uf[j]; uf[j] = i;
- }
+void linkSets(int a, int b) { // Union by size.
+ if (unions[b] > unions[a]) swap(a, b);
+ unions[b] += unions[a];
+ unions[a] = b;
}
-void unionSets(int i, int j) {
- if(findSet(i) != findSet(j)) linkSets(findSet(i),findSet(j));
+void unionSets(int a, int b) {
+ if (findSet(a) != findSet(b)) linkSets(findSet(a),findSet(b));
+}
+
+void getSize(int i) {
+ return -unions[findSet(i)];
}