70. Climbing Stairs

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?

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Dynamic Programming

Solution 1:

public class Solution {
public int climbStairs(int n) {
if(n <=2 )
return n;

int[] count = new int
;
count[0] = 1;
count[1] = 2;

return getCount(count, n-1);
}

private int getCount(int[] count, int index)
{
if(count[index] != 0)
return count[index];
int steps = getCount(count, index -1) + getCount(count, index -2);
count[index] = steps;
return steps;
}
}

Solution 2:

public class Solution {
public int climbStairs(int n) {
if(n <=2 )
return n;

int[] count = new int
;
count[0] = 1;
count[1] = 2;

for(int i =2; i< n; ++i)
{
count[i] = count[i-1]+count[i-2];
}

return count[n -1];
}
}