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Note: Given n will be a positive integer.
Example 1:
| Code Block |
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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:
| Code Block |
|---|
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++
| Code Block |
|---|
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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