feat: add subarray with given sum

src/array/subarray-with-given-sum/subarray-with-given-sum.test.ts

@@ -0,0 +1,17 @@
+import { subarrayWithGivenSum } from "./subarray-with-given-sum";
+
+describe("subarrayWithGivenSum", () => {
+  it.each([
+    { arr: [], target: 5, expected: [] },
+    { arr: [5], target: 5, expected: [0] },
+    { arr: [2, 3], target: 5, expected: [0, 1] },
+    { arr: [2, 3], target: 6, expected: [] },
+    { arr: [1, 2, 3, 7, 5], target: 12, expected: [1, 3] },
+    { arr: [1, 4, 20, 3, 10, 5], target: 33, expected: [2, 4] },
+  ])(
+    "returns $expected for arr = $arr and target = $target",
+    ({ arr, target, expected }) => {
+      expect(subarrayWithGivenSum(arr, target)).toEqual(expected);
+    }
+  );
+});

src/array/subarray-with-given-sum/subarray-with-given-sum.ts

@@ -0,0 +1,44 @@
+/**
+ * Finds a subarray of a given array that sums up to a given target and returns its indices.
+ * @param arr - the array of numbers
+ * @param target - the target sum
+ */
+export function subarrayWithGivenSum(arr: number[], target: number): number[] {
+  // If the array is empty, return an empty array.
+  if (arr.length === 0) {
+    return [];
+  }
+
+  // If the array has only one element, check if it is equal to the target.
+  if (arr.length === 1) {
+    return arr[0] === target ? [0] : [];
+  }
+
+  // If the array has two elements, check if either of them is equal to the target or if their sum is equal to the target.
+  if (arr.length === 2) {
+    if (arr[0] === target || arr[1] === target) {
+      return [arr[0] === target ? 0 : 1];
+    } else if (arr[0] + arr[1] === target) {
+      return [0, 1];
+    } else {
+      return [];
+    }
+  }
+
+  let start = 0;
+  let end = 0;
+  let sum = arr[0];
+
+  while (end < arr.length) {
+    if (sum === target) {
+      return [start, end];
+    } else if (sum < target) {
+      end++;
+      sum += arr[end];
+    } else {
+      sum -= arr[start];
+      start++;
+    }
+  }
+  return [];
+}