leetCode 70. Climbing Stairs | 动态规划

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?思考：

top	steps
1	1
2	2
3	3
4	5
5	8
6	13
...	...

从上面的分析可以看出，f(top) = f(top - 1) + f(top - 2)使用动态规划，确定当前登到第i级台阶可能的步数是几。然后在查看下一级i+1台阶的可能步数。

代码实现如下：

class Solution {
public:
int climbStairs(int n)
{
if (n <= 0)
return 0;
if (n <= 2)
return n;

int a[2] = {1,2};
int tmp = 0;
for (int i = 0; i < n - 2; ++i)
{
tmp = a[0] + a[1];
a[0] = a[1];
a[1] = tmp;
}

return tmp;
}
};

总结：
先确定当前的结果，然后转移。确定下一步的结果。依次转移，直到结果。
2016-08-31 16:17:16