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You are climbing a stair case. It takes n steps to reach to the top. |
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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:
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Input: 2 |
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Output: 2 |
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Explanation: There are two ways to climb to the top. |
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1. 1 step + 1 step |
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2. 2 steps |
Example 2:
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Input: 3 |
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Output: 3 |
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Explanation: There are three ways to climb to the top. |
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1. 1 step + 1 step + 1 step |
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2. 1 step + 2 steps |
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3. 2 steps + 1 step |
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Solution in C++
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class Solution { public: int climbStairs(int n) { if (n<=3) return n; int i1=2, i2=3; for(int i=4; i<n; i++) { int tmp=i1+i2; i1=i2; i2=tmp; } return i1+i2; } }; |
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