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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
难度：easy
题目：爬楼梯用例。要用 n 步才能到达顶端. 第次可以爬 1 或 2 步，有多少种爬上楼顶的方式？注意：n 是正整数。
思路：递归转迭代
Runtime: 2 ms, faster than 100.00% of Java online submissions for Climbing Stairs.Memory Usage: 25.4 MB, less than 93.69% of Java online submissions for Climbing Stairs.
public class Solution {
public int climbStairs(int n) {
if (n <= 1) {
return 1;
}
int num1 = 1, num2 = 1, result = num1 + num2;
for (int i = 1; i < n; i++) {
result = num1 + num2;
num1 = num2;
num2 = result;
}
return result;
}
}
