Subarray Sum Divisible by K (Leetcode 974)

Medium/Subarray Sum Divisible by K.java

@@ -0,0 +1,27 @@
+class Solution {
+    public int subarraysDivByK(int[] nums, int k) {
+        int count =0;
+        int sum =0;
+        int rem =0;
+        HashMap<Integer,Integer> map = new HashMap<>();
+        map.put(0,1); //initially sum is 0 and it appeared once already
+
+        for(int num:nums){
+            sum+=num;
+            rem=sum%k;
+
+            if(rem<0){
+                rem+=k; // if k=7 and rem = -2 then rem+k =2 and the gap betwen 2 and -5 is 7 which is divisible by 7
+            }
+            if(map.containsKey(rem)){
+                count+=map.get(rem);
+                map.put(rem, map.get(rem)+1);
+            }
+            else{
+                map.put(rem,1);
+            }
+        }
+        System.out.println(map.entrySet());
+        return count;
+    }
+}