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ClimbingStairs.java
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ClimbingStairs.java
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package by.andd3dfx.common;
import java.util.HashMap;
import java.util.Map;
/**
* <pre>
* <a href="https://leetcode.com/problems/climbing-stairs/description/">Task description</a>
*
* You are climbing a staircase. It takes n steps to reach the top.
* Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
*
* Example 1:
* Input: n = 2
* Output: 2
* Explanation: There are two ways to climb to the top.
* 1. 1 step + 1 step
* 2. 2 steps
*
* Example 2:
* Input: n = 3
* Output: 3
* Explanation: There are three ways to climb to the top.
* 1. 1 step + 1 step + 1 step
* 2. 1 step + 2 steps
* 3. 2 steps + 1 step
*
* Constraints:
* 1 <= n <= 45
* </pre>
*
* @see <a href="https://youtu.be/bjE3KQM4ko4">Video solution</a>
*/
public class ClimbingStairs {
private static final Map<Integer, Integer> cache = new HashMap<>() {{
put(0, 1);
put(1, 1);
}};
public static int calc(int n) {
if (cache.containsKey(n)) {
return cache.get(n);
}
var result = calc(n - 1) + calc(n - 2);
cache.put(n, result);
return result;
}
}