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g2601_2700.s2623_memoize.readme.md Maven / Gradle / Ivy

2623\. Memoize

Medium

Given a function `fn`, return a **memoized** version of that function.

A **memoized **function is a function that will never be called twice with the same inputs. Instead it will return a cached value.

You can assume there are **3 **possible input functions: `sum`**,** `fib`**, **and `factorial`**.**

*   `sum`accepts two integers `a` and `b` and returns `a + b`.
*   `fib`accepts a single integer `n` and returns `1` if `n <= 1` or `fib(n - 1) + fib(n - 2)` otherwise.
*   `factorial` accepts a single integer `n` and returns `1` if `n <= 1` or `factorial(n - 1) * n` otherwise.

**Example 1:**

**Input** "sum" ["call","call","getCallCount","call","getCallCount"] [[2,2],[2,2],[],[1,2],[]]

**Output:** [4,4,1,3,2]

**Explanation:** 

const sum = (a, b) => a + b; 

const memoizedSum = memoize(sum); 

memoizedSum(2, 2); // Returns 4. sum() was called as (2, 2) was not seen before. 

memoizedSum(2, 2); // Returns 4. However sum() was not called because the same inputs were seen before. 

// Total call count: 1 

memoizedSum(1, 2); // Returns 3. sum() was called as (1, 2) was not seen before. 

// Total call count: 2

**Example 2:**

**Input** "factorial" ["call","call","call","getCallCount","call","getCallCount"] [[2],[3],[2],[],[3],[]]

**Output:** [2,6,2,2,6,2]

**Explanation:** 

const factorial = (n) => (n <= 1) ? 1 : (n \* factorial(n - 1)); 

const memoFactorial = memoize(factorial); 

memoFactorial(2); // Returns 2. 

memoFactorial(3); // Returns 6. 

memoFactorial(2); // Returns 2. However factorial was not called because 2 was seen before.

// Total call count: 2 

memoFactorial(3); // Returns 6. However factorial was not called because 3 was seen before. 

// Total call count: 2

**Example 3:**

**Input** "fib" ["call","getCallCount"] [[5],[]]

**Output:** [8,1]

**Explanation:** fib(5) = 8 // Total call count: 1

**Constraints:**

*   0 <= a, b <= 105
*   `1 <= n <= 10`
*   at most 105 function calls
*   at most 105 attempts to access callCount
*   `input function is sum, fib, or factorial`