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Author: 10coder

ProductArray.java

@@ -0,0 +1,32 @@
+import java.util.Arrays;
+
+public class ProductArray {
+
+    //we do left to right product and store previous elements product in current index
+    //we need to do product from right and multiply with current value
+    //O(n)
+    //[1            2        3       4     5]
+    //[1            1       1*2    1*2*3 1*2*3*4]
+    //[*2*3*4*5   *3*4*5    *4*5   *5      *1 ]
+    public static int[] productExceptSelf(int[] nums) {
+        int[] res=new int[nums.length];
+        res[0]=1;
+        //left to right product
+        for(int i=1;i<nums.length;i++) {
+            res[i]=res[i-1]*nums[i-1];
+        }
+
+        int pro=1;
+        //right to left product
+        for(int i=nums.length-1;i>=0;i--) {
+            res[i]*=pro;
+            pro*=nums[i];
+        }
+        return res;
+    }
+
+    public static void main(String[] args) {
+        System.out.println("120,60,40,30,24 Expected " );
+         Arrays.stream(productExceptSelf(new int[]{1,2,3,4,5})).forEach(x->System.out.print(x+" "));
+    }
+}