[Solved] What is the output of this Swift code? var dict = ["a": 1, "b": 2] dict["c", default: 0] += 3 print(dict) | Swift

Swift - Collections

What is the output of this Swift code?

var dict = ["a": 1, "b": 2]
dict["c", default: 0] += 3
print(dict)

A["a": 1, "b": 2, "c": 3]

B["a": 1, "b": 2]

C["a": 1, "b": 2, "c": 0]

DRuntime error

Step-by-Step Solution

Solution:

Step 1: Understand default subscript usage
dict["c", default: 0] returns 0 if "c" is missing, then adds 3 and assigns back.
Step 2: Check dictionary after operation
Since "c" was missing, it is added with value 3.
Final Answer:
["a": 1, "b": 2, "c": 3] -> Option A
Quick Check:
Default subscript adds missing key with updated value [OK]

Quick Trick: Default subscript adds missing keys when mutated [OK]

Common Mistakes:

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