Create Find the Minimum Number of Fibonacci Numbers Whose Sum is K.java

Author: anthonyzhub

Find the Minimum Number of Fibonacci Numbers Whose Sum is K.java

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+// https://leetcode.com/problems/find-the-minimum-number-of-fibonacci-numbers-whose-sum-is-k/
+
+class Solution {
+    
+    public ArrayList<Integer> generateFib(int k) {
+        
+        // OBJECTIVE: Return a list of fibonacci numbers from 1 to k
+        
+        // Create a list
+        ArrayList<Integer> fib = new ArrayList<>();
+        fib.add(1);
+        fib.add(1);
+        
+        // Populate list
+        int num = 1;
+        while (num < k) {
+            
+            // Get the last 2 numbers
+            int numA = fib.get(fib.size() - 1);
+            int numB = fib.get(fib.size() - 2);
+            
+            // If new number is less than or equal to k, update num and add it to list
+            if (numA + numB <= k) {
+                num = numA + numB;
+                fib.add(num);
+            }
+            
+            // If new number is greater than k, exit loop
+            else {
+                break;
+            }
+        }
+        
+        return fib;
+    }
+    
+    public int findK(ArrayList<Integer> fib, int n, int target) {
+        
+        // OBJECTIVE: Return index of target or number closest to it
+        
+        // If target equals to 0, exit function
+        if (target == 0) {return 0;}
+        
+        // If target is greater than or equal to fib's last element, return it
+        if (target >= fib.get(n - 1)) {return n - 1;}
+        
+        // Create left and right pointers
+        int leftPtr = 0;
+        int rightPtr = n - 1;
+        
+        // Do binary search to find target in fib
+        while (leftPtr < rightPtr) {
+            
+            // Create a middle pointer
+            int midPtr = (int) (leftPtr + rightPtr) / 2;
+            
+            // If middle element is greater than target, move rightPtr
+            if (fib.get(midPtr) > target) {
+                rightPtr = midPtr;
+            }
+            
+            // If middle element is less than or equal to target, move leftPtr
+            else {
+                leftPtr = midPtr + 1;
+            }
+        }
+        
+        // Return left pointer
+        return leftPtr - 1;
+    }
+    
+    public int findMinFibonacciNumbers(int k) {
+        
+        // OBJECTIVE: Return the minimum number of fibonacci numbers whose sum is equal to k
+     
+        // If k equals to 1, return it
+        if (k == 1) {return 1;}
+        
+        // Generate a list of fibonacci numbers from 1 to k
+        ArrayList<Integer> fib = generateFib(k);
+        int n = fib.size();
+        
+        // If the last element equals to k, return 1
+        if (fib.get(n - 1) == k) {return 1;}
+        
+        // Create a variable to hold minimum number of fibonacci numbers
+        int minLen = 0;
+        
+        // Get minimum number of fibonacci numbers
+        while (k > 0) {
+            
+            // Find k (or value closest to k) in fib
+            int idx = findK(fib, n, k);
+            
+            // Increment minLen
+            minLen++;
+            
+            // Update k by subtracting idx element from it
+            k -= fib.get(idx);
+        }
+        
+        return minLen;
+    }
+}