Added 4Sum II.java

varunu28 · varunu28 · commit 46ba87a1694e · 2020-12-17T08:09:48.000-08:00
diff --git a/Medium/4Sum II.java b/Medium/4Sum II.java
@@ -0,0 +1,18 @@
+class Solution {
+  public int fourSumCount(int[] A, int[] B, int[] C, int[] D) {
+    int n = A.length;
+    Map<Integer, Integer> map = new HashMap<>();
+    for (int i = 0; i < n; i++) {
+      for (int j = 0; j < n; j++) {
+        map.put(A[i] + B[j], map.getOrDefault(A[i] + B[j], 0) + 1);
+      }
+    }
+    int count = 0;
+    for (int i = 0; i < n; i++) {
+      for (int j = 0; j < n; j++) {
+        count += map.getOrDefault(-1 * (C[i] + D[j]), 0);
+      }
+    }
+    return count;
+  }
+}
