js-concepts: leetcode prob.454 - 4Sum II

Author: baochau.dinh

LeetCode/454. 4Sum II/index.js

@@ -0,0 +1,21 @@
+var fourSumCount = function(nums1, nums2, nums3, nums4) {
+  let frequenceMap = {}
+  for (let i = 0; i < nums3.length; i++) {
+    for (let j = 0; j < nums4.length; j++) {
+      frequenceMap[nums3[i] + nums4[j]] = frequenceMap[nums3[i] + nums4[j]] + 1 || 1;
+    }
+  }
+
+  let result = 0;
+  for (let i = 0; i < nums1.length; i++) {
+      for (let j = 0; j < nums2.length; j++) {
+          if (frequenceMap[-nums1[i] - nums2[j]]) {
+            result += frequenceMap[-nums1[i] - nums2[j]]
+          }
+      }
+  }
+  
+  return result;
+};
+
+console.log(fourSumCount([0,1,-1], [-1,1,0], [0,0,1], [-1,1,1]))