Climbing Stairs Problem


Description

LeetCode Problem 70.

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:

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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:

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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


Sample C++ Code

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class Solution {
public:
    int climbStairs(int n) {
        int f1 = 1;
        int f2 = 2;
        
        if (n == 1)
            return f1;
        if (n == 2)
            return f2;
        
        int f;
        for (int i = 3; i <= n; i ++) {
            f = f1 + f2;
            f1 = f2;
            f2 = f;
        }
        
        return f;
    }
};




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