Two Sum Problem

src/main/kotlin/Main.kt

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+package main.kotlin
+
+import TwoSum
+
+fun main() {
+    println("What's your name?")
+    val name = readln()
+    println("Hello, $name!")
+
+    // Calling Two Sum class
+    val obj = TwoSum()
+    val result = obj.twoSum(nums = intArrayOf(1,2,3,4,5), target = 9)
+
+    println("Indices: ${result.joinToString(",")}")
+}

src/main/kotlin/ds-algo-leetcode/TwoSum.kt

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+class TwoSum {
+
+/*
+* Time Complexity O(n)
+* Space Complexity O(n)
+*
+* Step 1 : Declare a Map of Integers which will be used for comparison
+* Step 2 : Run through the array with index
+* Step 3 : Substract the current element from target sum and store it
+* Step 4 : Check if the complement present in the map
+* Step 5 : If present then create and return an array of Integers with the index
+*          of the current element and fetched value from map with the complement key
+* Step 6 : Otherwise set the map with current element as key and current index
+*          as value
+* Step 7 : Return an empty array by default
+* */
+
+    fun twoSum(nums: IntArray, target: Int): IntArray {
+        val seen = mutableMapOf<Int, Int>()
+
+        // using array with index as index and value both are required for computation
+        for((index, element) in nums.withIndex()){
+            val complement = target - element
+            if( complement in seen )
+                return intArrayOf(seen.get(complement)!!, index)
+            // setting the map with the current index
+            seen[element] = index
+        }
+        return intArrayOf()
+    }
+}