70. Climbing Stairs

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.

S: 坐标型DP

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