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Added bottom up approach

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This commit is contained in:
Varun Upadhyay
2017-09-04 14:40:12 -07:00
parent 0d4cfbabe6
commit 73e05940ea
1 changed files with 28 additions and 2 deletions
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30
Dynamic Programming/Fibonacci.java
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@ -18,7 +18,8 @@ public class Fibonacci {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int n = Integer.parseInt(br.readLine()); int n = Integer.parseInt(br.readLine());
System.out.println(fib(n)); // Returns 8 for n = 6 System.out.println(fibMemo(n)); // Returns 8 for n = 6
System.out.println(fibBotUp(n)); // Returns 8 for n = 6
} }
/** /**
@ -28,7 +29,7 @@ public class Fibonacci {
* Outputs the nth fibonacci number * Outputs the nth fibonacci number
**/ **/
public static int fib(int n) { public static int fibMemo(int n) {
if (map.containsKey(n)) { if (map.containsKey(n)) {
return map.get(n); return map.get(n);
} }
@ -45,5 +46,30 @@ public class Fibonacci {
return f; return f;
} }
/**
* This method finds the nth fibonacci number using bottom up
*
* @param n The input n for which we have to determine the fibonacci number
* Outputs the nth fibonacci number
**/
public static int fibBotUp(int n) {
Map<Integer,Integer> fib = new HashMap<Integer,Integer>();
for (int i=1;i<n+1;i++) {
int f = 1;
if (i<=2) {
f = 1;
}
else {
f = fib.get(i-1) + fib.get(i-2);
}
fib.put(i, f);
}
return fib.get(n);
}
} }