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 :
Input: n = 2
Output: 2
Explanation: There are two ways to climb to the top.
1. 1 step + 1 step
2. 2 steps
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
題目的要求是算排列組合，給一個n階梯，一次只能踏 1 或 2步，算出所有的組合。 n = 1 , result = 1 n = 2 , result = 1 + 1 n = 3 , result = 2 + 1 n = 4 , result = 3 + 2 n = 5 , result = 5 + 3 發現公式是 f(n) = f(n-1) + f(n-2)
public class Solution {
public int ClimbStairs(int n) {
if (n == 1 || n==2)
{
return n;
}
int prev = 1;
int cur = 2;
for (int i = 3; i <= n; i++)
{
int temp = cur;
cur = cur + prev;
prev = temp;
}
return cur;
}
}
