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/* tested with: echo '[000111][111111][001001][001111][001111]' | go run ch-2.go
* `-> example 3
* echo '[101010][010101][101010][010101]' | go run ch-2.go
* `-> example 1
*/
package main
import (
"os"
"bufio"
"fmt"
"strings"
"reflect"
)
func usage() {
fmt.Println( "Usage: echo [1101][1100][0111][1011]' | go run ch-2.go" )
}
// this function will ignore any other information but "0","1","]"
func getPointsFromMatrixLines (raw string) [][]int {
var rowsOut [][]int
// remove new lines separated by []
lines := strings.Split(raw, "\n")
joined := strings.Join(lines, "")
matrixlines := strings.Split(joined, "]")
for ln, line := range matrixlines {
x := 0
var points []int
// collect useful data only
for _, singleStr := range line {
switch string(singleStr) {
case "1":
points = append( points, x )
x++
case "0":
x++
case "[": // okay but not used
case " ":
default:
fmt.Fprintf( os.Stderr,
"Wrong character(%s) at row: %d\n",
singleStr, ln )
}
}
rowsOut = append( rowsOut, points )
}
return rowsOut
}
type FullHLine struct {
points []int
row int
}
func (hl FullHLine) Length() int {
return hl.points[len(hl.points)-1] - hl.points[0]
}
func (hl FullHLine) StartingPoint() int {
return hl.points[0]
}
type Rect struct {
rows []int
cols []int
}
func (rect Rect) NorthWest() (int, int) {
// ref: https://gobyexample.com/multiple-return-values
return rect.rows[0], rect.cols[0]
}
func (rect Rect) Area() int {
return len(rect.rows) * len(rect.cols)
}
func getSubHorizLinesFromHorizLines ( hlinesARow []FullHLine ) []FullHLine {
var subHlinesAtARow []FullHLine
for _, hline := range hlinesARow {
for hl := hline ;len(hl.points) > 0; hl.points = hl.points[1:] {
var pnts_so_far []int;
for _, pnt := range(hl.points) {
pnts_so_far = append(pnts_so_far, pnt)
subHlinesAtARow = append(subHlinesAtARow,
FullHLine {pnts_so_far, hline.row} )
}
}
}
return subHlinesAtARow
}
func getHorizLinesFromPoints ( pointsAtRows [][]int ) [][]FullHLine{
var hlinesAtRows [][]FullHLine
for r, points := range pointsAtRows {
// note: a point will be allowed as a line
// so we can make a vertical line later on
// and vertical line is regarded as a rectangle
// in my implementation
if len(points) == 0 {
continue // skip empty line
}
points = append(points, points[len(points)-1] + 2) // dummy
prev := points[0]
pnts := []int{prev}
var hlinesAtARow []FullHLine
for _, curr := range points[1:] {
if (curr - prev) == 1 {
pnts = append(pnts, curr)
} else {
if len(pnts) > 0 {
hlinesAtARow = append(hlinesAtARow,
FullHLine { pnts, r } )
}
pnts = []int{curr}
}
prev = curr
}
hlinesAtRows = append(hlinesAtRows,
getSubHorizLinesFromHorizLines(hlinesAtARow))
}
return hlinesAtRows
}
func findLargestRectanglesFromHorizLines (hlinesAtRows [][]FullHLine) []Rect {
var largestRects []Rect
largestArea := 0
/* note: checking procedure is similar to below
* 1 2 3 4 -> // each number represents row number
* 1 -> 1 2 -> 1 2 3 -> 1 2 3 4 // but intersection is decreasing
* 2 -> 2 3 -> 2 3 4 ->
* 3 -> 3 4 ->
* 4
*/
for
base, har := 0, hlinesAtRows;
len(har) > 0;
base, har = base+1, har[1:] {
intersects := har[0] // initial intersection is same as first row
var rows []int
candidates:
for offset, candi:= range har {
rows = append(rows, base+offset)
var inters []FullHLine
for _, hlc := range candi {
for _, hli := range intersects {
if hli.row != hlc.row &&
hlc.row - hli.row > 1 {
// ignore if not consecutive
continue;
}
if reflect.DeepEqual(
hlc.points, hli.points) {
//fmt.Println( base, ":", hlc, "~~", hli )
// keep intersection
inters = append(inters, hlc)
r_cp := rows
c_cp := hli.points
rect := Rect { r_cp,c_cp }
narea := rect.Area()
if narea == 1 {
// skip a point
continue
}
// compare with largest
// and update largest
// if needed
if largestArea < narea {
largestArea =
narea
largestRects =
[]Rect{rect}
//fmt.Println( "new largest", largestRects)
} else if largestArea ==
narea {
largestRects = append(
largestRects,
rect )
//fmt.Println( "update largest", largestRects)
}
} else {
// remove from intersec.
}
}
if len(inters) == 0 {
break candidates // no need to go further
} else {
copy(intersects, inters)
}
}
}
}
return largestRects
}
func main() {
reader := bufio.NewReader(os.Stdin)
matrixString, _ := reader.ReadString('')
pointsAtRows := getPointsFromMatrixLines(matrixString)
hlinesAtRows := getHorizLinesFromPoints(pointsAtRows)
//fmt.Println( hlinesAtRows )
largestRects := findLargestRectanglesFromHorizLines(hlinesAtRows)
if len(largestRects) == 0 {
fmt.Println("0 as no rectangle found")
os.Exit(1)
} else {
fmt.Fprintln(os.Stderr, "Area:", largestRects[0].Area())
for _, rect := range largestRects {
y, x := rect.NorthWest()
fmt.Fprintf(os.Stderr, "At: (r:%d,c:%d)\n", y, x)
for range rect.rows {
fmt.Print("1")
for range rect.cols[1:] {
fmt.Print(" 1")
}
fmt.Println("")
}
}
}
os.Exit(0)
}
|
