advent-of-code-2022/odin/day01/day01.odin

package day01

import "core:fmt"
import "core:os"
import "core:math"
import "core:strconv"
import "core:slice/heap"

scan_to_next :: proc(data: []byte, delim: byte, start_from: int) -> int {
    for idx := start_from; idx < len(data); idx += 1 {
        if data[idx] == '\n' {
            return idx
        }
    }
    return -1;
}

main_first_attempt :: proc () {
    // Read in input file.
    fh, errno := os.open("day01/calories-basic.input")
    if errno != os.ERROR_NONE {
        panic("Don't know what to do!")
    }
    defer os.close(fh)

    line_start := 0 
    line_end := -1
    repr := 0
    sum := 0
    max := -1
    content: []byte
    ok: bool
    content, ok = os.read_entire_file_from_handle(fh)
    if !ok { return; }

    for line_start < len(content) {

        if content[line_start] == '\n' {
            fmt.println(line_start, " starts a blank line: skipping to ", line_start + 1)
            // Case: line is blank
            // End summation; we are in a new group
            max = math.max(max, sum)

            // OK YOU NEED TO BE VERY CAREFUL WITH THIS! FIRST ODIN FOOTGUN!
            // This line used to be `sum := 0` instead of `sum = 0` and I
            // think that re-defined `sum` in this local scope because the
            // total sum at the end was way too high; it never got reset to 0
            // here. If you think about it, it makes sense... but I would think
            // the compiler might warn me that I was shadowing something from
            // ouside the scope...
            sum = 0

            // Go to next line
            line_start += 1
            continue
        } 

        line_end = scan_to_next(content, '\n', line_start + 1)
        fmt.println("Next line: ", line_start, " thru ", line_end)

        // Case: no newlines left
        if line_end == -1 {
            // Get last line
            slc := string(content[line_start:len(content)])
            repr, ok = strconv.parse_int(slc)
            if !ok {
                // Line doesn't have a number on it?
                // TODO Just ignore for now
            } else {
                fmt.println("Result: ", repr, " Current Sum: ", sum + repr)
                sum += repr
                max = math.max(max, sum)
                sum = 0
            }
            break
        } 

        // Case: Normal line with a number on it
        slc := string(content[line_start:line_end])
        fmt.println("Reading line: ", slc)
        repr, ok = strconv.parse_int(slc)
        if !ok {
            // Line doesn't have a number on it?
            // TODO Just ignore for now
        } else {
            fmt.println("Result: ", repr, " Current Sum: ", sum + repr)
            sum += repr
        }
        line_start = line_end + 1
    }
    fmt.println("Largest group is ", max);
}

split_lines :: proc(data: []byte, delimiter: byte) -> [dynamic][]byte {
    result: [dynamic][]byte
    prev := 0 
    idx: int
    for idx = 0; idx < len(data); idx += 1 {
        if data[idx] == delimiter {
            append(&result, data[prev:idx])
            prev = idx + 1
        }
    }
    if prev < idx {
        append(&result, data[prev:idx])
    }
    return result 
}

main :: proc() {
    if len(os.args) < 2 {
        fmt.printf("Usage: %s FILENAME\n", os.args[0])
        os.exit(-1)
    }
    fh, errno := os.open(os.args[1])
    if errno != os.ERROR_NONE {
        fmt.printf("Cannot open %s: %s\n", os.args[1], os.get_last_error_string())
        os.exit(-1)
    }
    defer os.close(fh)
    content, ok := os.read_entire_file_from_handle(fh)
    if !ok { 
        fmt.printf("Cannot read %s: %s\n", os.args[1], os.get_last_error_string())
        os.exit(-1)
    }
    lines := split_lines(content, '\n')
    total := 0
    mh := make([dynamic]int, context.temp_allocator)
    defer delete(mh)
    comparator :: proc(a, b: int) -> bool {
        return a < b
    }
    heap.make(mh[:], comparator)

    for line, idx in lines {
        if len(line) == 0 {
            append(&mh, total)
            heap.push(mh[:], comparator)
            total = 0
        } else {
            x: int
            s := string(line)
            x, ok = strconv.parse_int(s)
            if ok {
                total += x
            } else {
                fmt.eprintf("Line %d: not a valid integer\n", idx)
            }
        }
    }
    append(&mh, total)
    heap.make(mh[:], comparator)
    total = 0
    fmt.printf("Largest single value: %d\n", mh[0])
    for _ in 0..<3 {
        total += mh[0]
        heap.pop(mh[:], comparator)
    }
    fmt.printf("Sum of three largest: %d\n", total)
}