second solution

5kyu/smallest-possible-sum/solution.ts

@@ -1,20 +1,5 @@
-// idea: keep the array sorted
-// whenever we execute the subtraction, place the result in the correct position
-
-/**
- * Inserts the value in a sorted array to keep it sorted.
- * The sort direction is assumed to be ascending.
- * @param arr The sorted array
- * @param value The value to insert
- */
-const sortInsert = (arr: number[], value: number): void => {
-  let i = 0;
-  while (i < arr.length && arr[i] < value) {
-    i++;
-  }
-
-  arr.splice(i, 0, value);
-}
+// idea: find lowest number, subtract it from all other numbers,
+// repeat until all numbers are the same
 
 /**
  * Does a single operation on the given array.
@@ -24,24 +9,32 @@ const sortInsert = (arr: number[], value: number): void => {
 const operate = (arr: number[]): boolean => {
   // last element is the largest
   // find the first element that is not the largest
-  let i = arr.length - 1;
-  while (i >= 0 && arr[i] === arr[arr.length - 1]) {
-    i--;
+  const first = arr[0]; // smallest
+
+  // subtract as many multiples of the smallest number from all the rest
+  let i = 1;
+
+  // if all numbers are the same, return true
+  // if the array is sorted, it is enough to compare the first and last elements
+  if(arr[arr.length - 1] === first) return true;
+
+  while (i < arr.length) {
+    const div = arr[i] / first;
+    let flooredDiv = Math.floor(arr[i] / first);
+
+    if(flooredDiv === div && flooredDiv > 0) {
+      flooredDiv--;
+    }
+
+    const newValue = arr[i] - first * flooredDiv;
+    if (newValue !== 0) {
+      arr[i] = newValue;
+    }
+    i++;
   }
 
-  if (i < 0) {
-    // all elements are the same
-    return true;
-  }
-
-  // subtract
-  const value = arr[arr.length - 1] - arr[i];
-
-  // remove the last element
-  arr.pop();
-
-  // insert the value in the correct position
-  sortInsert(arr, value);
+  // sort the array
+  arr.sort((a, b) => a - b);
 
   return false;
 }

5kyu/smallest-possible-sum/tests.ts

@@ -3,6 +3,14 @@ import { assert } from "chai";
 
 import { solution } from "./solution";
 
-describe('Example test', function() {
-  it('[6,9,12]', () => assert.strictEqual(solution([6,9,21]),9));
+describe('Example test', function () {
+  it('[6,9,12]', () => assert.strictEqual(solution([6, 9, 21]), 9));
+  it('[1,21,55]', () => assert.strictEqual(solution([1, 21, 55]), 3));
+  it('[3,13,23,7,83]', () => assert.strictEqual(solution([3, 13, 23, 7, 83]), 5));
+  it('[4,16,24]', () => assert.strictEqual(solution([4, 16, 24]), 12));
+  it('[30,12]', () => assert.strictEqual(solution([30, 12]), 12));
+  it('[60,12,96,48,60,24,72,36,72,72,48]', () => assert.strictEqual(solution([60, 12, 96, 48, 60, 24, 72, 36, 72, 72, 48]), 132));
+  it('[71,71,71,71,71,71,71,71,71,71,71,71,71]', () => assert.strictEqual(solution([71, 71, 71, 71, 71, 71, 71, 71, 71, 71, 71, 71, 71]), 71 * 13));
+  it('[11,22]', () => assert.strictEqual(solution([11,22]), 22));
+  it('[9]', () => assert.strictEqual(solution([9]), 9));
 });