Climbing Stairs
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?
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Example 1:
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:
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
C++ Solution
首先发现规律f(n) = f(n-1) + f(n-2), 但是以递归的提交会导致超时， 所以以迭代的方式再实现如下：
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int climbStairs(int n) {
if (n == 1) {
return 1;
}
if (n == 2) {
return 2;
}
int left = 1;
int right = 2;
int cur = 0;
for (int i = 3; i <= n; i++) {
cur = left + right;
left = right;
right = cur;
}
return cur;
}
