Create 1286-iterator-for-combination.js

Author: everthis

1286-iterator-for-combination.js

@@ -0,0 +1,43 @@
+/**
+ * @param {string} characters
+ * @param {number} combinationLength
+ */
+const CombinationIterator = function (characters, combinationLength) {
+  this.arr = build(combinationLength, characters.split('').sort().join(''))
+  this.pos = 0
+}
+
+/**
+ * @return {string}
+ */
+CombinationIterator.prototype.next = function () {
+  if (this.pos < this.arr.length) {
+    return this.arr[this.pos++]
+  }
+}
+
+/**
+ * @return {boolean}
+ */
+CombinationIterator.prototype.hasNext = function () {
+  return this.pos < this.arr.length
+}
+
+/**
+ * Your CombinationIterator object will be instantiated and called as such:
+ * var obj = new CombinationIterator(characters, combinationLength)
+ * var param_1 = obj.next()
+ * var param_2 = obj.hasNext()
+ */
+function build(max, str, out = [], curr = '') {
+  if (curr.length === max) {
+    out.push(curr)
+    return
+  } else {
+    for (let i = 0; i < str.length; i++) {
+      build(max, str.slice(i + 1), out, curr + str[i])
+    }
+  }
+
+  return out
+}