[REFACTOR] [Hacker Rank] Interview Preparation Kit: Recursion: Davis'…

… Staircase. Problem rewritten as OOP to avoid "no-param-reassign". Clean code: better test cases data naming.

src/hackerrank/interview_preparation_kit/recursion_and_backtracking/ctci_recursive_staircase.test.ts

@@ -1,10 +1,7 @@
 import { describe, expect, it } from '@jest/globals';
 import { logger as console } from '../../../logger';
 
-import {
-  stepPerms,
-  step_perms_comput_with_cache
-} from './ctci_recursive_staircase';
+import { stepPerms, StepPerms } from './ctci_recursive_staircase';
 import TEST_CASES from './ctci_recursive_staircase.testcases.json';
 import TEST_CASES_GENERALIZED from './ctci_recursive_staircase_generalized.testcases.json';
 
@@ -14,9 +11,9 @@ describe('ctci_recursive_staircase', () => {
 
     TEST_CASES.forEach((testSet) => {
       testSet?.tests.forEach((test) => {
-        const answer = stepPerms(test.input);
+        const answer = stepPerms(test.n_steps);
 
-        console.debug(`stepPerms(${test.input}) solution found: ${answer}`);
+        console.debug(`stepPerms(${test.n_steps}) solution found: ${answer}`);
 
         expect(answer).toStrictEqual(test.expected);
       });
@@ -26,17 +23,16 @@ describe('ctci_recursive_staircase', () => {
   it('step_perms_comput_with_cache test cases', () => {
     expect.assertions(3);
 
+    const TOP_LIMIT = 10 ** 10 + 7;
+
     TEST_CASES_GENERALIZED.forEach((testSet) => {
       testSet?.tests.forEach((test) => {
-        const initial_cache: Record<number, number> = {};
-        const answer = step_perms_comput_with_cache(
-          test.input,
-          initial_cache,
-          test.limit
-        );
+        const stairs = new StepPerms(TOP_LIMIT, test.steps_limit);
+
+        const answer = stairs.step_perms_comput_with_cache(test.n_steps);
 
         console.debug(
-          `step_perms_comput_with_cache(${test.input}, ${initial_cache}, ${test.limit}) solution found: ${answer}`
+          `step_perms_comput_with_cache(${test.n_steps}, ${test.steps_limit}) solution found: ${answer}`
         );
 
         expect(answer).toStrictEqual(test.expected);

src/hackerrank/interview_preparation_kit/recursion_and_backtracking/ctci_recursive_staircase.testcases.json

@@ -1,49 +1,49 @@
 [
-    {
-        "title": "Sample Test case 0",
-        "tests": [
-            {
-                "input": 1,
-                "expected": 1
-            },
-            {
-                "input": 3,
-                "expected": 4
-            },
-            {
-                "input": 7,
-                "expected": 44
-            }
-        ]
-    },
-    {
-        "title": "Sample Test case 9",
-        "tests": [
-            {
-                "input": 5,
-                "expected": 13
-            },
-            {
-                "input": 8,
-                "expected": 81
-            }
-        ]
-    },
-    {
-        "title": "Sample Test case 10",
-        "tests": [
-            {
-                "input": 15,
-                "expected": 5768
-            },
-            {
-                "input": 20,
-                "expected": 121415
-            },
-            {
-                "input": 27,
-                "expected": 8646064
-            }
-        ]
-    }
+  {
+    "title": "Sample Test case 0",
+    "tests": [
+      {
+        "n_steps": 1,
+        "expected": 1
+      },
+      {
+        "n_steps": 3,
+        "expected": 4
+      },
+      {
+        "n_steps": 7,
+        "expected": 44
+      }
+    ]
+  },
+  {
+    "title": "Sample Test case 9",
+    "tests": [
+      {
+        "n_steps": 5,
+        "expected": 13
+      },
+      {
+        "n_steps": 8,
+        "expected": 81
+      }
+    ]
+  },
+  {
+    "title": "Sample Test case 10",
+    "tests": [
+      {
+        "n_steps": 15,
+        "expected": 5768
+      },
+      {
+        "n_steps": 20,
+        "expected": 121415
+      },
+      {
+        "n_steps": 27,
+        "expected": 8646064
+      }
+    ]
+  }
 ]

src/hackerrank/interview_preparation_kit/recursion_and_backtracking/ctci_recursive_staircase.ts

@@ -6,39 +6,41 @@
 const TOP_LIMIT = 10 ** 10 + 7;
 const STEPS_LIMIT = 3;
 
-export function step_perms_comput_with_cache(
-  n_steps: number,
-  cache: Record<number, number>,
-  steps_limit: number
-): number {
-  if (0 <= n_steps && n_steps <= 2) {
-    return n_steps;
+export class StepPerms {
+  TOP_LIMIT = 1;
+  STEPS_LIMIT = 1;
+  CACHE: Record<number, number> = {};
+
+  constructor(top_limit: number, steps_limit: number) {
+    this.TOP_LIMIT = top_limit;
+    this.STEPS_LIMIT = steps_limit;
   }
 
-  const keys = new Set(Object.values(cache));
-  let result = 0;
-
-  for (let i = 1; i <= Math.min(steps_limit, n_steps); i++) {
-    const searchKey = n_steps - i;
-    if (!keys.has(searchKey)) {
-      cache[searchKey] = step_perms_comput_with_cache(
-        searchKey,
-        cache,
-        steps_limit
-      );
+  step_perms_comput_with_cache(n_steps: number): number {
+    if (0 <= n_steps && n_steps <= 2) {
+      return n_steps;
     }
 
-    result += cache[searchKey];
-  }
+    const keys = new Set(Object.keys(this.CACHE));
+    let result = 0;
+
+    for (let i = 1; i <= Math.min(this.STEPS_LIMIT, n_steps); i++) {
+      const searchKey = n_steps - i;
+      if (!keys.has(searchKey.toString())) {
+        this.CACHE[searchKey] = this.step_perms_comput_with_cache(searchKey);
+      }
+
+      result += this.CACHE[searchKey];
+    }
 
-  return result + (n_steps <= steps_limit ? 1 : 0);
+    return result + (n_steps <= this.STEPS_LIMIT ? 1 : 0);
+  }
 }
 
 export function stepPerms(n: number): number {
-  const initial_cache: Record<number, number> = {};
-  return (
-    step_perms_comput_with_cache(n, initial_cache, STEPS_LIMIT) % TOP_LIMIT
-  );
+  const stairs = new StepPerms(TOP_LIMIT, STEPS_LIMIT);
+
+  return stairs.step_perms_comput_with_cache(n) % TOP_LIMIT;
 }
 
-export default { stepPerms, step_perms_comput_with_cache };
+export default { stepPerms, StepPerms };

src/hackerrank/interview_preparation_kit/recursion_and_backtracking/ctci_recursive_staircase_generalized.testcases.json

@@ -3,8 +3,8 @@
     "title": "Own sample 1",
     "tests": [
       {
-        "input": 4,
-        "limit": 3,
+        "n_steps": 4,
+        "steps_limit": 3,
         "expected": 7
       }
     ]
@@ -13,8 +13,8 @@
     "title": "Own sample 2",
     "tests": [
       {
-        "input": 5,
-        "limit": 4,
+        "n_steps": 5,
+        "steps_limit": 4,
         "expected": 15
       }
     ]
@@ -23,8 +23,8 @@
     "title": "Own sample 3",
     "tests": [
       {
-        "input": 6,
-        "limit": 2,
+        "n_steps": 6,
+        "steps_limit": 2,
         "expected": 13
       }
     ]