Climbing stairs: you can either climb one step or two steps at a time. How many different ways can you climb to the top?
Using a search approach would result in TLE. So I switched to an iterative approach:
a[n] = a[n-1] + a[n-2]
Accepted on the first try.
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| class Solution {
public:
int climbStairs(int n) {
// Note: The Solution object is instantiated only once and is reused by each test case.
int a1 = 1;
int a2 = 2;
if(n == 1)
{
return a1;
}
if(n == 2)
{
return a2;
}
int index = 3;
int before = a2;
int now = a1 + a2;
while(true)
{
if(index == n)
{
return now;
}
int tmp = before;
before = now;
now = tmp + before;
index++;
}
}
};
|