climbing stairs

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.

Solution

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public class  {
    
    public int climbStairs(int n) {
        int a = 1, b = 1;
        while(n-- > 0) {
            a = (b+=a) -a;
        }
        return a;
    }
}