Invert a Dictionary Practice Problem

This data science coding problem helps you practice Data Structures, invert a dictionary, and implementation skills. Read the problem statement, write your solution, and strengthen your understanding of Data Structures.

Problem ID: 88
Problem key: 88-invert-a-dictionary
URL: https://datacrack.app/solve/88-invert-a-dictionary
Difficulty: medium
Topic: Data Structures
Module: Python Fundamentals

Problem Statement

# 🧩 Invert a Dictionary

---

### 🎯 Goal
Dictionary inversion (swapping keys and values) is a common data transformation. In data science, this appears when reversing label encodings, inverting index mappings, or building reverse lookup tables.

---

### 🔍 What Is Inversion?
Swap every key-value pair so values become keys and keys become values:

```
{"a": 1, "b": 2, "c": 3}
→ {1: "a", 2: "b", 3: "c"}
```

For this problem, assume all values are unique (so the inversion is unambiguous).

---

### 💻 Task
Implement `invert_dict(d)`.

---

### 📥 Input
- `d`: dict with unique values

### 📤 Output
- A new dict with keys and values swapped

---

### 🧩 Starter Code
```python
def invert_dict(d):
    """
    Invert a dictionary (swap keys and values).

    Args:
        d (dict): Dictionary with unique values

    Returns:
        dict: Inverted dictionary {value: key}
    """
    inverted = {}
    for key, value in d.items():
        # 🧠 TODO: In inverted, store value as the key and key as the value
        pass
    return inverted
```

---

### 💡 Example
```python
invert_dict({"a": 1, "b": 2, "c": 3})
# Expected: {1: "a", 2: "b", 3: "c"}

invert_dict({"name": "Alice", "role": "engineer"})
# Expected: {"Alice": "name", "engineer": "role"}
```

---

### 🔑 Key Concepts
- `dict.items()` — iterate over key-value pairs as tuples
- Dict keys must be **hashable** — strings, ints, tuples are hashable; lists are not
- In ML: label encoders create `{"cat": 0, "dog": 1}`, and you need `{0: "cat", 1: "dog"}` to decode predictions

Starter Code

def invert_dict(d):
    """
    Invert a dictionary (swap keys and values).

    Args:
        d (dict): Dictionary with unique values

    Returns:
        dict: Inverted dictionary {value: key}
    """
    inverted = {}
    for key, value in d.items():
        # 🧠 TODO: In inverted, store value as the key and key as the value
        pass
    return inverted

Invert a Dictionary Practice Problem

Problem Statement

Starter Code

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