hard_tasks.json

{
  "tasks": [
    {
      "id": "recursive-flatten",
      "description": "Flatten deeply nested arrays into single array",
      "examples": [
        {"input": [[1,[2,[3,4]]],5], "expected_output": [1,2,3,4,5]},
        {"input": [[[1]],[[2]]], "expected_output": [1,2]}
      ]
    },
    {
      "id": "pivot-table",
      "description": "Transform array of {key,value} into object",
      "examples": [
        {"input": [{"k":"a","v":1},{"k":"b","v":2}], "expected_output": {"a":1,"b":2}},
        {"input": [{"k":"x","v":10}], "expected_output": {"x":10}}
      ]
    },
    {
      "id": "nested-sum",
      "description": "Sum all numbers in nested structure recursively",
      "examples": [
        {"input": {"a":1,"b":{"c":2,"d":{"e":3}}}, "expected_output": 6},
        {"input": {"x":[1,2,{"y":3}]}, "expected_output": 6}
      ]
    },
    {
      "id": "conditional-transform",
      "description": "Double numbers if positive, zero if negative",
      "examples": [
        {"input": [1,-2,3,-4,5], "expected_output": [2,0,6,0,10]},
        {"input": [-1,-1,2], "expected_output": [0,0,4]}
      ]
    },
    {
      "id": "join-arrays",
      "description": "Join two arrays by matching id field",
      "examples": [
        {
          "input": {"users":[{"id":1,"name":"a"},{"id":2,"name":"b"}],"scores":[{"id":1,"score":100},{"id":2,"score":200}]},
          "expected_output": [{"id":1,"name":"a","score":100},{"id":2,"name":"b","score":200}]
        }
      ]
    }
  ]
}