【LeetCode】Climbing Stairs

题目描述：

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?
dp解，dp[i]=dp[i-1]+dp[i-2]，当然要判定边界。
代码：

class Solution {
public:
int climbStairs(int n) {
vector<int> dp(n);
for (int i = 0; i < n; i++){
if (!i)
dp[i] = 1;
if (i == 1)
dp[i] = 1;
if (i - 1 >= 0)
dp[i] += dp[i - 1];
if (i - 2 >= 0)
dp[i] += dp[i - 2];
}
return dp[n - 1];
}
};