add 1286

Author: Ashwagandha-coder

contest/src/main/java/com/github/contest/Execute.kt

@@ -1,10 +1,10 @@
 package com.github.contest
 
 
+import com.github.contest.design.wrapper
 import com.github.contest.math.numberOfPowerfulInt
 import com.github.contest.slidingWindow.customStructure.rabinKarpMultiPattern
 import com.github.contest.slidingWindow.customStructure.slidingWindowClassic
-import com.github.contest.slidingWindow.longestSubarray
 import com.github.contest.strings.fullJustify
 import com.github.contest.strings.subStrHash
 import java.util.TreeMap
@@ -16,7 +16,7 @@ import java.util.TreeMap
 
 fun main() {
 
-    longestSubarray(intArrayOf(8, 2, 4, 7), 4).also { println(it) }
+    wrapper()
 }
 
 

contest/src/main/java/com/github/contest/design/DesignLeetcode.kt

@@ -205,4 +205,44 @@ class PeekingIterator(iterator: Iterator<Int>) : Iterator<Int> {
     override fun hasNext(): Boolean {
         return store.isNotEmpty()
     }
+}
+
+/**
+ * 1286. Iterator for Combination
+ */
+
+class CombinationIterator(characters: String, combinationLength: Int) {
+
+    private val store = mutableListOf<String>()
+
+    init {
+        combine(0, characters, StringBuilder(), store, combinationLength)
+    }
+
+    fun next(): String = store.removeFirst()
+
+    fun hasNext(): Boolean = store.isNotEmpty()
+
+    private fun combine(
+        index: Int,
+        str: String,
+        subset: StringBuilder,
+        store: MutableList<String>,
+        limit: Int
+    ) {
+
+        if (subset.length == limit) {
+            store.add(subset.toString())
+            return
+        }
+
+        if (index == str.length) return
+
+        subset.append(str[index])
+        combine(index + 1, str, subset, store, limit)
+
+        subset.deleteAt(subset.length - 1)
+        combine(index + 1, str, subset, store, limit)
+    }
+
 }