/
03.go
69 lines (63 loc) · 1.24 KB
/
03.go
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package main
func init() {
addSolutions(3, problem3)
}
func problem3(ctx *problemContext) {
var ns []int64
var numBits int
scanner := ctx.scanner()
for scanner.scan() {
if numBits == 0 {
numBits = len(scanner.text())
}
ns = append(ns, parseInt(scanner.text(), 2, 64))
}
ctx.reportLoad()
counts := make([]int, numBits)
for _, n := range ns {
for i := 0; i < numBits; i++ {
if n&(1<<i) > 0 {
counts[i]++
} else {
counts[i]--
}
}
}
var gamma int64
for i, c := range counts {
if c > 0 {
gamma += int64(1) << i
}
}
epsilon := ^gamma & (int64(1)<<numBits - 1)
ctx.reportPart1(gamma * epsilon)
ox := filterDiag(ns, numBits, true)
co2 := filterDiag(ns, numBits, false)
ctx.reportPart2(ox * co2)
}
func filterDiag(ns []int64, numBits int, most bool) int64 {
for i := numBits - 1; ; i-- {
if len(ns) == 1 {
return ns[0]
}
ns = filterDiag1(ns, i, numBits, most)
}
panic("not found")
}
func filterDiag1(ns []int64, i int, numBits int, most bool) []int64 {
var count int
for _, n := range ns {
if n&(1<<i) > 0 {
count++
} else {
count--
}
}
var filtered []int64
for _, n := range ns {
if (n&(1<<i) > 0 == (count >= 0)) == most {
filtered = append(filtered, n)
}
}
return filtered
}