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Author: WorkWithAfridi

Swift/DailyCodingProblemsWithSwift.playground/Pages/Day1004.xcplaygroundpage/Contents.swift

@@ -0,0 +1,45 @@
+//This problem was asked by Goldman Sachs.
+//
+//Given a list of numbers L, implement a method sum(i, j) which returns the sum from the sublist L[i:j] (including i, excluding j).
+//
+//For example, given L = [1, 2, 3, 4, 5], sum(1, 3) should return sum([2, 3]), which is 4.
+//
+//You can assume that you can do some pre-processing. sum() should be optimized over the pre-processing step.
+
+class SumMap{
+    var list: [Int] = []
+    var sumAtIndexMap: [Int:Int] = [:]
+    var sum = 0
+    var count = 0
+    
+    func addInt(integer: Int) {
+        list.append(integer)
+        sum += integer
+        sumAtIndexMap[count] = sum
+        count += 1
+    }
+    
+    func getSum(i: Int, j: Int) -> Int {
+        print(sumAtIndexMap)
+        if i < list.count, j < list.count {
+            var ithVal : Int = (sumAtIndexMap[j] ?? 0)
+            var jthVal : Int = (sumAtIndexMap[i] ?? 0)
+            print("ithVal: \(ithVal)")
+            print("jthVal: \(jthVal)")
+            return ithVal - jthVal
+        }
+        return 0
+    }
+}
+
+
+var sumMap: SumMap = SumMap()
+
+sumMap.addInt(integer: 1) // 0
+sumMap.addInt(integer: 2) // 1
+sumMap.addInt(integer: 3) // 2
+sumMap.addInt(integer: 4) // 3
+sumMap.addInt(integer: 5) // 4
+
+var sumVal = sumMap.getSum(i: 2, j: 3)
+print("SumVal is \(sumVal)")

Swift/DailyCodingProblemsWithSwift.playground/contents.xcplayground

@@ -8,5 +8,6 @@
         <page name='Day1047'/>
         <page name='Day1050'/>
         <page name='SmallestDifference'/>
+        <page name='Day1004'/>
     </pages>
 </playground>