70. Climbing Stairs

最新推荐文章于 2024-01-18 13:59:59 发布

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最新推荐文章于 2024-01-18 13:59:59 发布

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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?

class Solution {
public:
    int climbStairs(int n) {
        if(n<=0)
         return 0;
        if(n==1)
         return 1;
        if(n==2)
         return 2;
        int i1=1,i2=2,i3=0;
        n-=2;
        while(n)
        {
            --n;
            i3=i1+i2;
            i1=i2;
            i2=i3;
        }
        return i3;
    }
};