Keep a little lookup notebook
Picture
Write “park: 5 minutes” in your notebook. Later, look up the park and find 5. A dictionary pairs a key with a value.
Predict
Our notebook says park: 5 and café: 8. What do we get by looking up park?
Let's look
- We use the key “park” to find its value.
A little Python, if you want it
minutes = {"park": 5, "cafe": 8}
assert minutes["park"] == 5
minutes["park"] = 6
assert minutes["park"] == 6A key has one current value. Assigning to that key again replaces its value. A dictionary can be a saved-answer notebook, provided the key really identifies the question.
Change one rule
Walking time changes with the starting place. Is the destination alone a good key?
Let's try it
Not always. You might use (start, destination) so different journeys don’t overwrite one another.
Connect
DP will reuse saved answers. First, draw places and the paths between them.