added function

Author: mauricechouam

Relative Sort Array/code.js

@@ -0,0 +1,29 @@
+/*
+ * @param {number[]} arr1
+ * @param {number[]} arr2
+ * @return {number[]}
+ */
+var relativeSortArray = function(arr1, arr2) {
+    const hash = {};
+    const remaining = []
+    for(let n of arr2){
+      hash[n] = hash[n] >= 0 ? hash[n] + 1 : 0
+    }
+    
+    for(let n of arr1){
+      hash[n] =  hash[n] >= 0 ? hash[n] + 1 : undefined
+      if(hash[n] === undefined) remaining.push(n)
+    }  
+    
+    remaining.sort((a,b)=>a-b)
+    
+    for(let i = 0; i < arr2.length; i++){
+      const curr = arr2[i]
+      if(hash[curr]-- > 1){
+        arr2.splice(i,0,curr)
+        i--
+      }
+    }
+    return arr2.concat(remaining)
+  };
+