**DAY9:**

This one felt good, for me. There are many loops, as you'll see. That is mainly because I had to write some utility functions for typical slice evaluation that Go doesn't have by default like other languages (*not complaining, just pointing out.*).

I do advise you split out the logic into helper functions. It could've gotten really messy if I did all of the work in the main function.

```
package days
import (
"fmt"
inputs "../inputs"
)
// https://adventofcode.com/2020/day/9
// Nine : advent of code, day nine part1 and 2
func Nine() {
inputSlice := inputs.Day9
part1 := getRuleBreaker(inputSlice, 25)
fmt.Print("(Part 1) - Value that doesn't follow preamble rule: ")
fmt.Println(part1)
part2 := contiguousCheckSum(inputSlice, part1)
fmt.Print("(Part 2) - Contiguous series sum (series max+min): ")
fmt.Println(part2)
}
func getRuleBreaker(inputSlice []int, preambleSize int) int {
for i := preambleSize; i < len(inputSlice); i++ {
preamble := inputSlice[i-preambleSize : i]
if !preambleEquator(preamble, inputSlice[i]) {
return inputSlice[i]
}
}
return 0
}
func contiguousCheckSum(inputSlice []int, toSum int) int {
maxMinSum := 0
for i := 0; i < len(inputSlice); i++ {
for j := i + 1; j < len(inputSlice); j++ {
if toSum != inputSlice[i] && toSum != inputSlice[j] {
contiguousSeries := inputSlice[i:j]
contSum := 0
for c := 0; c < len(contiguousSeries); c++ {
contSum = contSum + contiguousSeries[c]
}
if contSum == toSum {
maxMinSum = maxMinSumation(contiguousSeries)
}
}
}
}
return maxMinSum
}
func maxMinSumation(contiguousSeries []int) int {
min := contiguousSeries[0]
for v := 0; v < len(contiguousSeries); v++ {
if contiguousSeries[v] < min {
min = contiguousSeries[v]
}
}
max := contiguousSeries[0]
for v := 0; v < len(contiguousSeries); v++ {
if contiguousSeries[v] > max {
max = contiguousSeries[v]
}
}
return min + max
}
func preambleEquator(preamble []int, current int) bool {
worked := false
for j := 0; j < len(preamble); j++ {
for x := j + 1; x < len(preamble); x++ {
if preamble[j]+preamble[x] == current {
worked = true
break
}
}
}
return worked
}
```

## Top comments (0)