Question
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?
Stats
| Frequency | 5 |
| Difficulty | 2 |
| Adjusted Difficulty | 1 |
| Time to use | -------- |
Ratings/Color = 1(white) 2(lime) 3(yellow) 4/5(red)
Analysis
This is an easy DP question.
Solution
My code is simple and concise, better than any other.
So I posted it below.
My code
Original code
public int climbStairs(int n) {
if (n == 1) return 1;
if (n == 2) return 2;
int a = 1;
int b = 2;
int sum = 0;
for (int i=3 ; i<=n ; i++){
sum = a + b;
a = b;
b = sum;
}
return sum;
}
Optimized code
public int climbStairs(int n) {
if (n == 1) return 1;
int a = 1;
int sum = 1;
for (int i=2 ; i<=n ; i++){
sum += a;
a = sum - a;
}
return sum;
}