7) almost increasing sequence

Author: Jakub Jirous

README.md

@@ -21,7 +21,7 @@ In preparation for technical interviews, I discovered this platform that provide
 4) [Adjacent Elements Product](/src/arcade/intro/04-adjacent-elements-product/)
 5) [Shape Area](/src/arcade/intro/05-shape-area/)
 6) [Make Array Consecutive](/src/arcade/intro/06-make-array-consecutive/)
-
+7) [Almost Increasing Sequence](/src/arcade/07-almost-increasing-sequence/)
 
 ---
 

src/arcade/intro/07-almost-increasing-sequence/almost-increasing-sequence.test.ts

@@ -0,0 +1,37 @@
+import { almostIncreasingSequence } from "./almost-increasing-sequence";
+
+type FirstArg = number[];
+type ExpectedResult = boolean;
+type Cases = [FirstArg, ExpectedResult][];
+
+/**
+ * Tests whether it is possible to obtain a strictly increasing sequence by removing no more than one element from the array.
+ */
+describe("Almost Increasing Sequence", () => {
+  const cases: Cases = [
+    [[1, 3, 2, 1], false],
+    [[1, 3, 2], true],
+    [[1, 2, 1, 2], false],
+    [[3, 6, 5, 8, 10, 20, 15], false],
+    [[1, 4, 10, 4, 2], false],
+    [[10, 1, 2, 3, 4, 5], true],
+    [[0, -2, 5, 6], true],
+    [[1, 2, 3, 4, 5, 3, 5, 6], false],
+    [[40, 50, 60, 10, 20, 30], false],
+    [[1, 1], true],
+    [[1, 2, 5, 3, 5], true],
+    [[10, 1, 2, 3, 4, 5, 6, 1], false],
+    [[1, 2, 3, 4, 3, 6], true],
+    [[1, 2, 3, 4, 99, 5, 6], true],
+    [[123, -17, -5, 1, 2, 3, 12, 43, 45], true],
+    [[3, 5, 67, 98, 3], true],
+  ];
+
+  test.each(cases)(
+    "for sequence = %s output should be %s",
+    (firstArg, expectedResult) => {
+      const result = almostIncreasingSequence(firstArg);
+      expect(result).toEqual(expectedResult);
+    }
+  );
+});

src/arcade/intro/07-almost-increasing-sequence/almost-increasing-sequence.ts

@@ -0,0 +1,31 @@
+/**
+ * Given a sequence of integers as an array, determine whether it is possible to obtain a strictly increasing sequence by removing no more than one element from the array.
+ *
+ * Note: sequence a0, a1, ..., an is considered to be a strictly increasing if a0 < a1 < ... < an.
+ * Sequence containing only one element is also considered to be strictly increasing.
+ *
+ * Example:
+ * - For sequence = [1, 3, 2, 1], the output should be solution(sequence) = false.
+ * - There is no one element in this array that can be removed in order to get a strictly increasing sequence.
+ *
+ * - For sequence = [1, 3, 2], the output should be solution(sequence) = true.
+ * - You can remove 3 from the array to get the strictly increasing sequence [1, 2]. Alternately, you can remove 2 to get the strictly increasing sequence [1, 3].
+ *
+ * @param sequence
+ */
+export const almostIncreasingSequence = (sequence: number[]): boolean => {
+  let sequenceInterruptions = 0;
+
+  for (let i = 1; i < sequence.length; i++) {
+    if (sequence[i - 1] > sequence[i]) {
+      sequenceInterruptions++;
+
+      if (sequenceInterruptions > 1) return false;
+
+      if (sequence[i - 1] >= sequence[i + 1] && sequence[i - 2] >= sequence[i])
+        return false;
+    }
+  }
+
+  return true;
+};