Aggregate data with maps
Group and count values using map lookups and updates.
- Use Go maps to build per-key totals and frequencies.
A map in Go stores key-value pairs and is ideal for grouped summaries like counts per tag or totals per region. Use the “comma ok” form (value, ok := map[key]) to handle missing keys safely.
1package main
2
3import "fmt"
4
5func main() {
6 counts := map[string]int{}
7 counts["go"]++
8 counts["go"]++
9 fmt.Println(counts["go"])
10}2
Map iteration order is not guaranteed. If output format matters, print keys in a fixed order or sort them first. Deterministic output keeps tests and downstream integrations stable.
Key takeaways
Use Go maps to build per-key totals and frequencies.
Go catches many mistakes while compiling.
Use small experiments to understand each new language feature.
Lesson quiz
4 questions · pass with 3 correct · up to 50 XP
Passing this quiz completes the lesson and keeps your streak going. Questions you miss come back in review sessions later.
Practice: write Go
Write Go in the editor and run it against sample input with a remote compiler. Your code is sent to Compiler Explorer to compile and run.
Count Go tags
Read a count and then that many tags. Print how many times go appears.
- Two go tags
- No go tag
Go is compiled and run by Compiler Explorer (godbolt.org), a free public service. Your source code and test input are sent to that service.
Questions about this lesson
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