Desicription
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:
1
2
3
4
5
6
|
Input: 2
Output: 2
Explanation: There are two ways to climb to the top.
1. 1 step + 1 step
2. 2 steps
|
Example 2:
1
2
3
4
5
6
7
|
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
|
Solution
1
2
3
4
5
6
7
8
9
10
|
class {
public:
int climbStairs(int n) {
long long a = 1;
long long b = 1;
while(n--)
a = (b += a) - a;
return a;
}
};
|
近期评论