AOC_03

package main

import (
    "bufio"
    "fmt"
    "os"
    "strconv"
)

func findValue(sl *[]string, ox bool) {
    var c byte
    if ox {
        c = '1'
    } else {
        c = '0'
    }
    if sl != nil && len(*sl) > 0 {
        size := len((*sl)[0])

        for i := 0; i < size && len(*sl) != 1; i++ {
            var z = make([]string, 0)
            // Check common bit //
            count := 0

            for _, s := range *sl {
                if s[i] == c {
                    count++
                }
            }
            var flag bool
            if ox {
                flag = 2*count >= len(*sl)
            } else {
                flag = 2*count > len(*sl)
            }

            // Save with bit criteria //
            for _, s := range *sl {
                if flag && s[i] == '1' || !flag && s[i] == '0' {
                    z = append(z, s)
                }
            }

            *sl = z
        }
    }
}

func main() {
    fin, _ := os.Open("input.txt")
    defer fin.Close()

    scan := bufio.NewScanner(fin)
    file := make([]string, 0)
    count := 0
    var counters []int
    var gamma []byte
    var epsilon []byte

    var size int
    for scan.Scan() {
        str := scan.Text()
        file = append(file, str)

        if count == 0 {
            size = len(str)
            counters = make([]int, size)
            gamma = make([]byte, size)
            epsilon = make([]byte, size)
        }

        for i := 0; i < size; i++ {
            if str[i] == '1' {
                counters[i]++
            }
        }

        count++
    }

    // Calc gamma & epsilon

    for i := 0; i < size; i++ {
        if counters[i] > count/2 {
            gamma[i] = '1'
            epsilon[i] = '0'
        } else {
            gamma[i] = '0'
            epsilon[i] = '1'
        }
    }

    g := string(gamma[:])
    e := string(epsilon[:])

    gi, _ := strconv.ParseUint(g, 2, size)
    ei, _ := strconv.ParseUint(e, 2, size)

    fmt.Printf("gamma * epsilon = %d\n", gi*ei)

    /////////////////////////////////////////////////////////////////////////////
    // Second Part //////////////////////////////////////////////////////////////
    var slOx []string = make([]string, len(file))
    var slCO2 []string = make([]string, len(file))

    copy(slOx, file)
    copy(slCO2, file)

    findValue(&slOx, true)
    findValue(&slCO2, false)

    // Print values
    sNum := slOx[0]
    oxRate, _ := strconv.ParseUint(sNum, 2, size)
    fmt.Printf("Oxygen generator rating = %d\n", oxRate)

    sNum = slCO2[0]
    co2Rate, _ := strconv.ParseUint(sNum, 2, size)
    fmt.Printf("CO2 scrubber rating = %d\n", co2Rate)

    fmt.Printf("Life support rating = %d\n", oxRate*co2Rate)
}