Aggregate a Large Dataset With GROUP BY
Alpaca● EasyFULLTIMEPHONE SCREENProblem statement
Implement the core of SELECT key, SUM(value) ... GROUP BY key. The arrays describe rows in a large dataset: row i has grouping key keys[i] and integer measure values[i].
Return one string key=sum for every distinct key, sorted lexicographically by key. Use wide integer accumulation so group totals do not overflow a 32-bit sum.
Function
groupBySum(keys: String[], values: int[]) → String[]Examples
Example 1
keys = ["west","east","west","north"]values = [5,7,-2,4]return = ["east=7","north=4","west=3"]Rows are accumulated by key and formatted in key order.
Example 2
keys = ["a","a","b"]values = [1000000000,1000000000,-3]return = ["a=2000000000","b=-3"]The same group can contain large and negative values.
Constraints
0 <= keys.length = values.length <= 200000- Keys are nonempty strings of length at most 100.
-10^9 <= values[i] <= 10^9