contest problem #1

Author: zq29

Franklin/maximumProduct.java

@@ -0,0 +1,42 @@
+/*
+lc contest 38, problem 1
+Given an array of integers, return the maximum product of three elements in the array.
+Spec: Array length >=3, element in the range [-1000, 1000].
+*/
+public class Solution {
+    public int maximumProduct(int[] nums) {
+        int product = Integer.MIN_VALUE;
+        List<Integer> pos = new ArrayList();
+        List<Integer> neg = new ArrayList();
+        for (int i=0; i<nums.length; i++) {
+            if (nums[i]>0) {pos.add(nums[i]);}
+            else {neg.add(nums[i]);}
+            
+        }
+        Collections.sort(pos);
+        Collections.sort(neg, Collections.reverseOrder());
+        
+        // two cases
+        int result = Integer.MIN_VALUE;
+        
+        if (pos.size()==0) {
+            result = neg.get(neg.size()-1)*neg.get(neg.size()-2)*neg.get(neg.size()-3);
+        } else if (pos.size()==1) {
+            result = pos.get(pos.size()-1) * neg.get(neg.size()-1)*neg.get(neg.size()-2);
+        } else if (pos.size()==2) {
+            if (neg.size()>=2)
+                result = pos.get(pos.size()-1) * neg.get(neg.size()-1) * neg.get(neg.size()-2);
+            else if (neg.size()==1)
+                result = nums[0]*nums[1]*nums[2];
+        } else if (pos.size()>=3) {
+            if (neg.size()<=1) {
+                result = pos.get(pos.size()-1)*pos.get(pos.size()-2)*pos.get(pos.size()-3);
+            } else if (neg.size()>=2) {
+                int neg_prod = neg.get(neg.size()-1)*neg.get(neg.size()-2);
+                int pos_prod = pos.get(pos.size()-2)*pos.get(pos.size()-3);
+                result = pos.get(pos.size()-1)*Integer.max(pos_prod,neg_prod);
+            }
+        }
+        return result;
+    }
+}