Create disjoint_union_set.cpp

Classic disjoint set union data structure in c++.

algorithms/CPlusPlus/DisjointSetUnion/disjoint_set_union.cpp

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+#include<bits/stdc++.h>
+using namespace std;
+
+/*
+Disjoint set union data structure supporting find and union operations.
+Time Complexity: O(a(N)) where a(N) is the Inverse Ackerman function.
+*/
+const int N=1e3;
+vector<int>P(N),S(N);
+
+// create new node
+void create(int u){
+    P[u]=u;S[u]=1;
+}
+// find parent of node
+int find(int u){
+    if(u==P[u])return u;
+    return P[u]=find(P[u]);
+}
+// merge 2 nodes
+void merge(int u,int v){
+    u=find(u);
+    v=find(v);
+    if(u!=v){
+        if(S[u]<S[v]){
+            P[u]=v;
+            S[v]+=S[u];
+        }else{
+            P[v]=u;
+            S[u]+=S[v];
+        }
+    }
+}