Added Hash Table

RashikAnsar · RashikAnsar · commit 4b252c078c12 · 2018-10-25T09:32:57.000+05:30
diff --git a/data-structures/hashTable.js b/data-structures/hashTable.js
@@ -0,0 +1,76 @@
+/**
+ * @author Rashik Ansar
+ *
+ * Implementation of Hash Table
+ */
+
+class HashTable {
+  constructor(size = 47) {
+    this.keyMap = new Array(size);
+  }
+
+  /**
+   * Hash Function
+   * Private method to generate hash of the given data
+   * @param {*} key data to hash
+   */
+  _hash(key) {
+    let total = 0;
+    const RANDOM_PRIME = 31;
+    for (let i = 0; i < Math.min(key.length, 100); i++) {
+      let char = key[i];
+      let value = char.charCodeAt(0) - 96;
+      total = (total * RANDOM_PRIME + value) % this.keyMap.length;
+    }
+    return total;
+  }
+
+  set(key, value) {
+    let index = this._hash(key);
+    if (!this.keyMap[index]) {
+      this.keyMap[index] = [];
+    }
+    this.keyMap[index].push([key, value]);
+    return this;
+  }
+
+  get(key) {
+    let index = this._hash(key);
+    if (this.keyMap[index]) {
+      for (let i = 0; i < this.keyMap[index].length; i++) {
+        if (this.keyMap[index][i][0] === key) {
+          return this.keyMap[index][i];
+        }
+      }
+    }
+    return undefined;
+  }
+
+  values() {
+    let valArray = [];
+    for (let i = 0; i < this.keyMap.length; i++) {
+      if (this.keyMap[i]) {
+        for (let j = 0; j < this.keyMap[i].length; j++) {
+          if (!valArray.includes(this.keyMap[i][j][1])) {
+            valArray.push(this.keyMap[i][j][1]);
+          }
+        }
+      }
+    }
+    return valArray;
+  }
+
+  keys() {
+    let keysArray = [];
+    for (let i = 0; i < this.keyMap.length; i++) {
+      if (this.keyMap[i]) {
+        for (let j = 0; j < this.keyMap[i].length; j++) {
+          if (!keysArray.includes(this.keyMap[i][j][0])) {
+            keysArray.push(this.keyMap[i][j][0]);
+          }
+        }
+      }
+    }
+    return keysArray;
+  }
+}
