Add disjoint set data structure

Data-Structures/Disjoint Set/DisjointSet.js

@@ -0,0 +1,77 @@
+class DisjointSet {
+  constructor() {
+    this.parents = {};
+    this.ranks = {};
+    this.sizes = {};
+  }
+
+  // initializes a disjoint set
+  makeSet(x) {
+    this.parents[x] = x;
+    this.ranks[x] = 0;
+    this.sizes[x] = 1;
+  }
+
+  // returns the ultimate parent of the node.
+  find(x) {
+    if (this.parents[x] !== x) {
+      this.parents[x] = this.find(this.parents[x]);
+    }
+    return this.parents[x];
+  }
+
+  // method to combine two nodes by rank.
+  unionByRank(x, y) {
+    let rootX = this.find(x);
+    let rootY = this.find(y);
+
+    if (rootX === rootY) return;
+
+    if (this.ranks[rootX] < this.ranks[rootY]) {
+      this.parents[rootX] = rootY;
+    } else if (this.ranks[rootX] > this.ranks[rootY]) {
+      this.parents[rootY] = rootX;
+    } else {
+      this.parents[rootY] = rootX;
+      this.ranks[rootX]++;
+    }
+  }
+
+  // method to combine two nodes by size.
+  unionBySize(x, y) {
+    let rootX = this.find(x);
+    let rootY = this.find(y);
+
+    if (rootX === rootY) return;
+
+    if (this.sizes[rootX] < this.sizes[rootY]) {
+      [rootX, rootY] = [rootY, rootX];
+    }
+
+    this.parents[rootY] = rootX;
+    this.sizes[rootX] += this.sizes[rootY];
+  }
+}
+
+//   // Example usage:
+//   const ds = new DisjointSet();
+//   ds.makeSet(1);
+//   ds.makeSet(2);
+//   ds.makeSet(3);
+
+//   ds.unionByRank(1, 2);
+//   ds.unionByRank(2, 3);
+
+//   console.log(ds.find(1)); // Output: 1
+//   console.log(ds.find(2)); // Output: 1
+//   console.log(ds.find(3)); // Output: 1
+
+//   ds.makeSet(4);
+//   ds.makeSet(5);
+
+//   ds.unionBySize(4, 5);
+//   ds.unionBySize(1, 4);
+
+//   console.log(ds.find(4)); // Output: 1
+//   console.log(ds.find(5)); // Output: 1
+//   console.log(ds.sizes[1]); // Output: 5