Problem #11

Problem link
Solution:

package main

import (
    "strconv"
    "io/ioutil"
    "strings"
)

func main() {
    fileBuf, err := ioutil.ReadFile("011_input.txt")
    if err != nil {
        panic(err.String())
    }
    fileStr := string(fileBuf)
    lines := strings.Split(fileStr, "\n", 20)
    arr := make([][]uint, 20)
    var strArr []string
    for i := range lines {
        arr[i] = make([]uint, 20)
        strArr = strings.Split(lines[i], " ", 20)
        for j := range arr[i] {
            intvalue, _ := strconv.Atoi(strArr[j])
            arr[i][j] = uint(intvalue)
        }
    }
    max := uint(0)
    //left to right
    for i := range arr {
        for j := 0; j < 17; j++ {
            mul := arr[i][j] * arr[i][j+1] * arr[i][j+2] * arr[i][j+3]
            if mul > max {
                max = mul
            }
        }
    }
    //up to down
    for i := 0; i < 17; i++ {
        for j := range arr[i] {
            mul := arr[i][j] * arr[i+1][j] * arr[i+2][j] * arr[i+3][j]
            if mul > max {
                max = mul
            }
        }
    }
    //first diagonal
    for i := 0; i < 17; i++ {
        for j := 0; j < 17; j++ {
            mul := arr[i][j] * arr[i+1][j+1] * arr[i+2][j+2] * arr[i+3][j+3]
            if mul > max {
                max = mul
            }
        }
    }
    //second diagonal
    for i := 3; i < 20; i++ {
        for j := 0; j < 17; j++ {
            mul := arr[i][j] * arr[i-1][j+1] * arr[i-2][j+2] * arr[i-3][j+3]
            if mul > max {
                max = mul
            }
        }
    }
    println(max)
}

Input file is renamed as 011_input.txt.

Result: 70600674
Time: 0m0.005s

Problem #13

Problem link
Solution:

package main

import (
    "io/ioutil"
    "strconv"
    "strings"
)

func main() {
    fileBuf, err := ioutil.ReadFile("013_input.txt")
    if err != nil {
        panic(err.String())
    }
    fileStr := string(fileBuf)
    lines := strings.Split(fileStr, "\n", 100)
    result := ""
    carryout, digit := 0, 0
    for i := 49; i >= 0; i-- {
        sum := carryout
        for j := range lines {
            num, _ := strconv.Atoi(string(lines[j][i]))
            sum += num
        }
        digit = sum % 10
        carryout = sum / 10
        result = strconv.Itoa(digit) + result
    }
    result = strconv.Itoa(carryout) + result
    println(result[0:10])
}

Result: 5537376230
Time: 0m0.010s

Problem #18

Problem link
Solution:

package main

import (
    "io/ioutil"
    "strconv"
    "strings"
)

var arr [][]int
var bests [][]int

func main() {
    fileBuf, err := ioutil.ReadFile("018_input.txt")
    if err != nil {
        panic(err.String())
    }
    fileStr := strings.Trim(string(fileBuf), "")
    oneDArrStr := strings.Split(fileStr, "\n", -1)
    var line []string
    arr = make([][]int, 15)
    bests = make([][]int, len(arr))
    for i := range arr {
        line = strings.Split(oneDArrStr[i], " ", -1)
        arr[i] = make([]int, len(line))
        bests[i] = make([]int, len(arr[i]))
        for j := range line {
            arr[i][j], _ = strconv.Atoi(line[j])
            bests[i][j] = -1
        }
    }
    println(bestSum(0, 0))
}

func bestSum(i, j int) int {
    var result int
    if bests[i][j] != -1 {
        result = bests[i][j]
    } else if i == len(arr)-1 {
        result = arr[i][j]
        return arr[i][j]
    } else {
        sumLeft, sumRight := bestSum(i+1, j), bestSum(i+1, j+1)
        if sumLeft > sumRight {
            result = arr[i][j] + sumLeft
        } else {
            result = arr[i][j] + sumRight
        }
    }
    bests[i][j] = result
    return result
}

Tree is read from a file named as 018_input.txt and also memoization is used for this problem.

Result: 1074
Time: 0m0.005s

Problem #22

Problem link
Solution:

package main

import (
    "io/ioutil"
    "strings"
    "sort"
)

func main() {
    fileBuf, err := ioutil.ReadFile("022_input.txt")
    if err != nil {
        panic(err.String())
    }
    fileStr := string(fileBuf)
    arr := strings.Split(fileStr, ",", -1)
    for i := range arr {
        arr[i] = strings.Split(arr[i], "\"", -1)[1]
    }

    sort.SortStrings(arr)

    result := uint64(0)
    for i := range arr {
        result += uint64(i+1) * uint64(alphabeticValue(arr[i]))
    }
    println(result)
}

func alphabeticValue(in string) int {
    sum := 0
    for i := range in {
        sum += int(in[i]) - int('A') + 1
    }
    return sum
}

Result: 871198282
Time: 0m0.035s

Problem #42

Problem link
Solution:

package main

import (
    "io/ioutil"
    "strings"
)

var triangles []int

func main() {
    //read names
    fileBuf, err := ioutil.ReadFile("042_input.txt")
    if err != nil {
        panic(err.String())
    }
    fileStr := string(fileBuf)
    arr := strings.Split(fileStr, ",", -1)
    for i := range arr {
        arr[i] = strings.Split(arr[i], "\"", -1)[1]
    }

    //create an array of triangle numbers
    triangles = make([]int, 20)
    for i := range triangles {
        triangles[i] = (i * (i + 1)) / 2
    }

    //iterate over names to check
    result := 0
    for i := range arr {
        if isTriangle(alphabeticValue(arr[i])) {
            result++
        }
    }
    println(result)
}

func isTriangle(in int) bool {
    for i := range triangles {
        if triangles[i] == in {
            return true
        }
    }
    return false
}

func alphabeticValue(in string) int {
    sum := 0
    for i := range in {
        sum += int(in[i]) - int('A') + 1
    }
    return sum
}

Result: 162
Time: 0m0.009s