Fibonacci number
Title: asked to enter an integer n, you output the n-th Fibonacci term of Number of
A1: Textbook method, recursive, but the time complexity increases with the increment n ====> impractical
A2: intermediate columns can be saved items obtained up to avoid double counting ====> time complexity of O (n)
A3: Data formula (too advanced, do not understand)
// O (n) method, save intermediate term
class Solution {
public:
int Fibonacci(int n) {
int ret[] = {0,1};
if(n <= 1)
{
return ret[n];
}
long long fib_1 = 0;
long long fib_2 = 1;
long long fib_n = 0;
for(int i = 2; i <= n ;i++)
{
fib_n = fib_1 + fib_2;
fib_1 = fib_2;
fib_2 = fib_n;
}
return fib_n;
}
};
Related topics:
Summing (input two integers n and m, l, 2,3 random number sequence taken from several ....... number n, and it is equal to m, which requires all of the possible combinations listed)
Looking for the K-large (there is an array of integers, you sort of the quick thinking to find a large array of K number.)
Generating a Gray code (encoding a set of numbers, if any two adjacent code only one bit different, this encoding is called Gray code (Gray Code), a write request function, using the recursive method of generating N-bit Gray code. given an integer n , return to an n-bit Gray code, of the order of from zero.)
Frog jump stairs
Title: A frog can jump on a Class 1 level, you can also hop on level 2. The frog jumped seeking a total of n grade level how many jumps (the order of different calculation different results).
class Solution {
public:
int jumpFloor(int number) {
if(number <= 2)
{
return number;
}
long long number_1 = 1;
long long number_2 = 2;
long long number_n = 0;
for (int i = 3; i <= number; i++)
{
number_n = number_1 + number_2;
number_1 = number_2;
number_2 = number_n;
}
return number_n;
}
};
Related topics:
A rectangular cover (2 * with a small rectangle to cover a larger rectangle, ask by small rectangles 8 2 1 * non-overlapping coverage of a large rectangle 2 * 8, the total number of ways)
Stairs (in front of you there is a n-order staircase, you can only step on the first-order or second order. Will calculate how many different ways you can use climbed the stairs.)
2 stairs (before you have a staircase n-th order (n> = 100 and n <500), you can only step 1 and 3rd order. Will calculate how many different ways that you can use the stairs climbed (the last layer as Pawan))