move to 4kyu

4kyu/smallest-possible-sum/solution.ts

@@ -0,0 +1,59 @@
+// idea: do not ever sort
+// simply keep looping from left to right and back to left
+// whenever a smaller number is found,
+// subtract as many multiples of that number from the rest of the array
+
+const subtractMultiples = (a: number, b: number): number => {
+  // subtract a from b as many times as possible
+  const mod = b % a;
+  if (mod === 0) {
+    // figure out how many times a can be subtracted from b
+    const div = b / a - 1;
+    return b - a * div;
+  } else {
+    return mod;
+  }
+}
+
+const operate = (arr: number[]): boolean => {
+
+  let step = 1;
+  let i = 0;
+  let done = false;
+  let hasChangedDuringLoop = false;
+  while (!done) {
+    if (i + step >= arr.length || i + step < 0) {
+      // reverse direction
+      step = -step;
+      if (!hasChangedDuringLoop) {
+        done = true;
+      }
+      hasChangedDuringLoop = false;
+    }
+
+    const first = arr[i];
+    const next = arr[i + step];
+
+    if (first > next) {
+      arr[i] = subtractMultiples(next, first);
+      hasChangedDuringLoop = true;
+    } else if (first < next) {
+      arr[i + step] = subtractMultiples(first, next);
+      hasChangedDuringLoop = true;
+    }
+
+    i += step;
+  }
+
+  return true;
+}
+
+export function solution(numbers: number[]): number {
+  let done = false;
+  while (!done) {
+    done = operate(numbers);
+  }
+
+  // sum the numbers
+  return numbers.reduce((acc, num) => acc + num, 0);
+}