70. Climbing Stairs
题目
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
解析
// add 70. Climbing Stairs
class Solution_70 {
public:
int climbStairs(int n) {
int ret = 0;
int f1 = 1, f2 = 2;
if (n == 1 || n == 2)
{
return n;
}
for (int i = 3; i <= n;i++)
{
int temp = f1 + f2;
f1 = f2;
f2 = temp;
}
return f2;
}
int climbStairs_(int n)
{
if (n==1||n==2)
{
return n;
}
return climbStairs_(n - 1) + climbStairs_(n - 2);
}
};
题目来源
