### LeetCode - Climbing Stairs Java - The Coding Shala

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## LeetCode Climbing Stairs Problem

In this post, we will see how to solve the leetcode climbing stairs problem in Java.

You are climbing a stair-case. It takes n steps to reach to the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
Note: Given n will be a positive integer.

Example 1:

Input: 2

Output: 2

Explanation: There are two ways to climb to the top.

1. 1 step + 1 step

2. 2 steps

Example 2:
Input: 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

## Climbing Stairs Java Solution

Approach 1:

Using dynamic programming.

Java Program:

```class Solution {
public int climbStairs(int n) {
if(n<=2) return n;
int[] dp = new int[n];
dp[0] = 1;
dp[1] = 2;
for(int i=2;i<n;i++){
dp[i] = dp[i-1]+dp[i-2];
}
return dp[n-1];
}
}
```

Approach 2:
Using Recursion.
Java Program:

```class Solution {
HashMap<Integer, Integer> map = new HashMap<>();
public int climbStairs(int n) {
if(map.containsKey(n)){
return map.get(n);
}

int result;
if(n<=2) result = n;
else{
result = climbStairs(n-1)+climbStairs(n-2);
}
map.put(n,result);
return result;
}
}
```

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