70. Climbing Stairs

Problem:

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

思路：

Solution (C++):

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

性能：

Runtime: 0 ms  Memory Usage: 6.2 MB

思路：

Solution (C++):

性能：

Runtime: ms  Memory Usage: MB