👉 A Tour of Go : Exercise - Maps
Implement WordCount
This is probably bread-and-butter for any seasoned programmer, but I enjoyed the simple process and satisfaction of breaking the problem down into steps to solve using what the tutorial had just covered. Sketching out the logic in pseudo-code first, I figured that I wanted to do this:
-
For each word in the phrase:
- Check if the word exists in the map already
- Create it if it doesn’t
- Add one to the map value
- Check if the word exists in the map already
Using Printf it was useful to check on how it was executing.
func WordCount(s string) map[string]int {
w := make(map[string]int)
for i, v := range strings.Fields(s) {
fmt.Printf("Index: %d value %v\n",i, v)
if _, o := w[v]; o == true {
fmt.Printf("\tExisting map found for %v with value %d\n",v,w[v])
w[v] = w[v] + 1
} else {
fmt.Printf("\tCreating new map for %v with value 1\n",v)
w[v] = 1
}
}
return w
}
I liked that the tutorial uses tests to check what you’ve done, and shows the expected output:
PASS
f("I am learning Go!") =
map[string]int{"Go!":1, "I":1, "am":1, "learning":1}
PASS
f("The quick brown fox jumped over the lazy dog.") =
map[string]int{"The":1, "brown":1, "dog.":1, "fox":1, "jumped":1, "lazy":1, "over":1, "quick":1, "the":1}
PASS
f("I ate a donut. Then I ate another donut.") =
map[string]int{"I":2, "Then":1, "a":1, "another":1, "ate":2, "donut.":2}
PASS
f("A man a plan a canal panama.") =
map[string]int{"A":1, "a":2, "canal":1, "man":1, "panama.":1, "plan":1}
Looking at the pseudo-code and what Golang will handle for you automagically it can be reduced to this:
-
For each word in the phrase:
-
Check if the word exists in the map alreadyCreate it if it doesn’t
- Add one to the map value (implicitly create the map entry if it doesn’t already exist)
-
func WordCount(s string) map[string]int {
w := make(map[string]int)
for _, v := range strings.Fields(s) {
w[v] = w[v] + 1
}
return w
}
Note: the underscore character, representing a required variable that you’re not going to use, is pretty useful.
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