Created
September 9, 2019 20:25
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| import java.math.BigInteger; | |
| public class Fibonacci { | |
| private int fib1(int n) { | |
| if (n == 1 || n == 2) { | |
| return 1; | |
| } | |
| int r = fib1(n - 1) + fib1(n - 2); | |
| return r; | |
| } | |
| private BigInteger fib2(int n, BigInteger[] memo) { | |
| if (memo == null) { | |
| memo = new BigInteger[n + 1]; | |
| } | |
| if (memo[n] != null) { | |
| return memo[n]; | |
| } | |
| if (n == 1 || n == 2) { | |
| return BigInteger.ONE; | |
| } | |
| BigInteger r = fib2(n - 1, memo).add(fib2(n - 2, memo)); | |
| memo[n] = r; | |
| return r; | |
| } | |
| private BigInteger fibBottomUp(int n) { | |
| if (n == 1 || n == 2) { | |
| return BigInteger.ONE; | |
| } | |
| BigInteger[] memo = new BigInteger[n + 1]; | |
| memo[1] = BigInteger.ONE; | |
| memo[2] = BigInteger.ONE; | |
| for (int i = 3; i <= n; i++) { | |
| memo[i] = memo[i - 1].add(memo[i - 2]); | |
| } | |
| return memo[n]; | |
| } | |
| public static void main(String[] args) { | |
| Fibonacci fibonacci = new Fibonacci(); | |
| //Recursion solution | |
| System.out.println(fibonacci.fib1(15));//after 50 fail | |
| //Store solution | |
| System.out.println(fibonacci.fib2(9200, null));//fail StackOverflowError after 9255 | |
| //Bottom up solution | |
| System.out.println(fibonacci.fibBottomUp(200000));//fail Java heap space after 250000 | |
| } | |
| } |
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