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Optimized Version [Without Hashmap & recursion] #649

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Merged
yanglbme merged 1 commit into from
Nov 26, 2018
Merged

Optimized Version [Without Hashmap & recursion] #649

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34 changes: 34 additions & 0 deletions Dynamic Programming/Fibonacci.java
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,10 @@ public static void main(String[] args) throws Exception {
* Outputs the nth fibonacci number
**/





private static int fibMemo(int n) {
if (map.containsKey(n)) {
return map.get(n);
Expand Down Expand Up @@ -71,5 +75,35 @@ private static int fibBotUp(int n) {

return fib.get(n);
}



/**
* This method finds the nth fibonacci number using bottom up
*
* @author Shoaib Rayeen (https://github.com/shoaibrayeen)
* @param n The input n for which we have to determine the fibonacci number
* Outputs the nth fibonacci number
*
* This is optimized version of Fibonacci Program. Without using Hashmap and recursion.
* It saves both memory and time.
* Space Complexity will be O(1)
* Time Complexity will be O(n)
*
* Whereas , the above functions will take O(n) Space.
**/
private static int fibOptimized(int n) {

if (n == 0) {
return 0;
}
int prev = 0 , res = 1 , next;
for ( int i = 2; i < n; i++) {
next = prev + res;
prev = res;
res = next;
}
return res;
}
}