diff --git a/2021/day04/input b/2021/day04/input
new file mode 100644
index 0000000..780a141
--- /dev/null
+++ b/2021/day04/input
@@ -0,0 +1,601 @@
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diff --git a/2021/day04/main.go b/2021/day04/main.go
new file mode 100644
index 0000000..cb20a59
--- /dev/null
+++ b/2021/day04/main.go
@@ -0,0 +1,197 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	inp := h.StdinToStringSlice()
+	boards := buildBoards(inp[1:])
+	draws := parseDraws(inp[0])
+	//part1(boards, draws)
+	part2(boards, draws)
+}
+
+func part1(boards []Board, draws []int) {
+	var winners []Board
+	for i := range draws {
+		for b := range boards {
+			if boards[b].Mark(draws[i]) {
+				winners = append(winners, boards[b])
+			}
+		}
+		if len(winners) > 0 {
+			break
+		}
+	}
+	for w := range winners {
+		fmt.Println("# Part 1")
+		fmt.Println(winners[w])
+		fmt.Println(winners[w].Score())
+		fmt.Println()
+	}
+}
+
+func part2(boards []Board, draws []int) {
+	var winners []Board
+	for i := range draws {
+		for b := range boards {
+			if boards[b].Mark(draws[i]) {
+				winners = append(winners, boards[b])
+			}
+		}
+		// Remove all winners from boards
+		for i := range winners {
+			for b := range boards {
+				if winners[i].String() == boards[b].String() {
+					boards = append(boards[:b], boards[b+1:]...)
+					break
+				}
+			}
+		}
+
+		if len(boards) == 0 {
+			break
+		}
+	}
+	fmt.Println("# Part 2")
+	fmt.Println("Last Winner")
+	fmt.Println(winners[len(winners)-1])
+	fmt.Println(winners[len(winners)-1].Score())
+	fmt.Println()
+}
+
+func parseDraws(inp string) []int {
+	var ret []int
+	pts := strings.Split(inp, ",")
+	for i := range pts {
+		ret = append(ret, h.Atoi(pts[i]))
+	}
+	return ret
+}
+
+type Spot struct {
+	value  int
+	marked bool
+}
+
+type Board struct {
+	spots map[h.Coordinate]Spot
+	draws []int
+}
+
+func NewBoard(inp []string) Board {
+	b := Board{
+		spots: make(map[h.Coordinate]Spot),
+	}
+	for y := range inp {
+		row := strings.Fields(strings.TrimSpace(inp[y]))
+		for x := range row {
+			v := h.Atoi(row[x])
+			b.spots[h.Coordinate{X: x, Y: y}] = Spot{value: v}
+		}
+	}
+	return b
+}
+
+func buildBoards(inp []string) []Board {
+	var boards []Board
+	var boardStr []string
+	for i := range inp {
+		if inp[i] == "" {
+			// start/end of a board
+			if len(boardStr) == 5 {
+				boards = append(boards, NewBoard(boardStr))
+			}
+			boardStr = []string{}
+		} else {
+			boardStr = append(boardStr, inp[i])
+		}
+	}
+	if len(boardStr) == 5 {
+		boards = append(boards, NewBoard(boardStr))
+	}
+
+	return boards
+}
+
+// Mark adds a number to the draws and returns whether this board has won
+func (b *Board) Mark(v int) bool {
+	b.draws = append(b.draws, v)
+	for k := range b.spots {
+		s := b.spots[k]
+		if b.spots[k].value == v {
+			s.marked = true
+			b.spots[k] = s
+			return b.Won()
+		}
+	}
+	return b.Won()
+}
+
+func (b *Board) Won() bool {
+	for y := 0; y < 5; y++ {
+		if b.CheckRowForWin(y) {
+			return true
+		}
+	}
+	for x := 0; x < 5; x++ {
+		if b.CheckColForWin(x) {
+			return true
+		}
+	}
+	return false
+}
+
+func (b *Board) CheckRowForWin(y int) bool {
+	for x := 0; x < 5; x++ {
+		if b.spots[c(x, y)].marked == false {
+			return false
+		}
+	}
+	return true
+}
+
+func (b *Board) CheckColForWin(x int) bool {
+	for y := 0; y < 5; y++ {
+		if b.spots[c(x, y)].marked == false {
+			return false
+		}
+	}
+	return true
+}
+
+func (b *Board) Score() int {
+	var unmarked int
+	for y := 0; y < 5; y++ {
+		for x := 0; x < 5; x++ {
+			if b.spots[c(x, y)].marked == false {
+				unmarked += b.spots[c(x, y)].value
+			}
+		}
+	}
+	return unmarked * b.draws[len(b.draws)-1]
+}
+
+func (b Board) String() string {
+	var ret string
+	for y := 0; y < 5; y++ {
+		for x := 0; x < 5; x++ {
+			c := c(x, y)
+			marked := " "
+			if b.spots[c].marked {
+				marked = "X"
+			}
+			ret = fmt.Sprintf("%s%s: %2d[%v]  ", ret, c, b.spots[c].value, marked)
+		}
+		ret = ret + "\n"
+	}
+	return ret
+}
+
+func c(x, y int) h.Coordinate {
+	return h.Coordinate{X: x, Y: y}
+}
diff --git a/2021/day04/testinput b/2021/day04/testinput
new file mode 100644
index 0000000..669a51d
--- /dev/null
+++ b/2021/day04/testinput
@@ -0,0 +1,19 @@
+7,4,9,5,11,17,23,2,0,14,21,24,10,16,13,6,15,25,12,22,18,20,8,19,3,26,1
+
+22 13 17 11  0
+ 8  2 23  4 24
+21  9 14 16  7
+ 6 10  3 18  5
+ 1 12 20 15 19
+
+ 3 15  0  2 22
+ 9 18 13 17  5
+19  8  7 25 23
+20 11 10 24  4
+14 21 16 12  6
+
+14 21 17 24  4
+10 16 15  9 19
+18  8 23 26 20
+22 11 13  6  5
+ 2  0 12  3  7
diff --git a/2021/day05/input b/2021/day05/input
new file mode 100644
index 0000000..e988a9e
--- /dev/null
+++ b/2021/day05/input
@@ -0,0 +1,500 @@
+644,38 -> 644,265
+941,468 -> 941,89
+807,552 -> 618,363
+896,510 -> 896,744
+227,909 -> 227,745
+24,66 -> 946,988
+563,529 -> 563,270
+894,707 -> 359,172
+146,253 -> 146,569
+544,683 -> 140,683
+755,612 -> 755,463
+394,320 -> 891,320
+68,616 -> 68,628
+801,770 -> 801,942
+650,290 -> 580,360
+376,18 -> 181,213
+285,391 -> 805,911
+57,153 -> 501,153
+686,301 -> 686,316
+81,971 -> 683,369
+75,456 -> 75,355
+769,59 -> 769,81
+49,958 -> 49,718
+492,754 -> 492,256
+606,133 -> 391,133
+134,683 -> 134,656
+195,463 -> 658,926
+982,498 -> 982,927
+841,122 -> 889,74
+968,891 -> 968,189
+104,941 -> 104,868
+801,450 -> 272,979
+212,749 -> 212,366
+880,928 -> 880,757
+503,483 -> 283,263
+792,924 -> 792,540
+58,87 -> 905,934
+275,661 -> 36,422
+475,654 -> 466,645
+34,946 -> 969,11
+725,664 -> 725,150
+837,680 -> 837,952
+109,987 -> 644,452
+860,984 -> 860,691
+672,800 -> 107,235
+216,888 -> 301,888
+399,676 -> 718,357
+957,544 -> 784,544
+677,743 -> 633,743
+491,866 -> 77,452
+967,949 -> 45,27
+659,699 -> 659,27
+987,116 -> 696,116
+465,847 -> 309,847
+353,19 -> 353,627
+265,713 -> 592,386
+541,765 -> 461,765
+21,409 -> 895,409
+950,149 -> 766,149
+856,889 -> 895,889
+335,962 -> 485,812
+425,774 -> 400,749
+71,932 -> 989,14
+484,974 -> 44,974
+86,797 -> 86,470
+876,962 -> 876,384
+45,631 -> 169,507
+161,789 -> 523,427
+791,640 -> 791,581
+415,170 -> 835,590
+299,275 -> 988,964
+105,233 -> 231,359
+202,226 -> 202,958
+814,717 -> 618,521
+185,442 -> 559,68
+26,149 -> 665,149
+673,369 -> 247,795
+171,963 -> 171,46
+689,801 -> 94,206
+619,243 -> 619,637
+426,245 -> 660,11
+47,503 -> 47,179
+341,363 -> 487,217
+371,774 -> 371,871
+781,794 -> 781,180
+391,632 -> 92,632
+517,150 -> 517,715
+903,10 -> 18,895
+34,500 -> 426,500
+82,955 -> 886,151
+142,297 -> 142,527
+60,965 -> 36,965
+250,807 -> 372,685
+227,393 -> 610,776
+269,893 -> 269,556
+969,223 -> 611,223
+255,92 -> 194,92
+220,233 -> 958,233
+144,209 -> 144,979
+48,413 -> 48,195
+209,151 -> 648,590
+867,648 -> 871,644
+499,555 -> 807,555
+571,729 -> 865,435
+683,151 -> 485,151
+803,26 -> 803,691
+533,921 -> 300,688
+625,695 -> 483,553
+719,370 -> 139,950
+981,17 -> 16,982
+367,617 -> 367,636
+249,644 -> 835,644
+260,825 -> 260,519
+275,144 -> 275,315
+767,314 -> 962,119
+76,625 -> 76,166
+403,680 -> 313,680
+977,21 -> 16,982
+578,753 -> 271,753
+212,358 -> 477,623
+596,220 -> 868,220
+67,797 -> 935,797
+181,107 -> 181,379
+741,332 -> 419,10
+732,827 -> 732,989
+835,111 -> 436,510
+480,328 -> 480,682
+327,673 -> 327,70
+911,547 -> 833,625
+944,509 -> 874,579
+169,340 -> 731,902
+156,842 -> 825,173
+976,40 -> 51,965
+199,416 -> 916,416
+51,970 -> 792,229
+14,577 -> 501,577
+246,464 -> 246,289
+641,464 -> 100,464
+984,11 -> 43,952
+548,36 -> 156,428
+519,799 -> 519,43
+332,364 -> 332,774
+85,123 -> 85,753
+778,12 -> 40,750
+507,56 -> 507,840
+973,632 -> 670,632
+895,928 -> 37,70
+661,784 -> 661,718
+114,25 -> 938,849
+428,752 -> 428,543
+357,270 -> 957,870
+27,70 -> 899,942
+85,780 -> 747,780
+717,565 -> 951,565
+191,748 -> 651,748
+679,301 -> 679,417
+150,266 -> 150,184
+774,964 -> 64,254
+34,248 -> 34,279
+782,610 -> 802,610
+109,146 -> 822,859
+825,848 -> 825,666
+251,718 -> 615,718
+912,722 -> 289,722
+729,579 -> 729,889
+214,756 -> 214,716
+58,497 -> 58,927
+62,55 -> 742,55
+110,429 -> 110,154
+55,794 -> 638,794
+182,96 -> 676,96
+632,334 -> 202,764
+36,541 -> 36,397
+191,819 -> 191,277
+971,491 -> 839,491
+849,561 -> 538,250
+176,523 -> 10,689
+162,638 -> 717,638
+132,843 -> 646,329
+873,67 -> 873,389
+167,631 -> 167,473
+49,337 -> 465,337
+550,429 -> 438,429
+305,720 -> 476,720
+547,636 -> 547,902
+21,627 -> 49,627
+286,70 -> 989,70
+87,930 -> 896,121
+659,916 -> 200,916
+234,589 -> 234,308
+530,962 -> 90,962
+366,478 -> 676,788
+284,520 -> 284,546
+580,74 -> 146,508
+561,977 -> 561,237
+85,150 -> 804,869
+740,850 -> 159,269
+458,705 -> 458,639
+969,563 -> 381,563
+139,439 -> 139,263
+135,971 -> 908,198
+440,632 -> 102,632
+446,549 -> 446,734
+24,49 -> 212,237
+692,882 -> 527,882
+156,895 -> 156,239
+359,246 -> 359,603
+12,349 -> 604,941
+375,161 -> 732,161
+674,287 -> 322,287
+902,957 -> 328,383
+352,185 -> 352,766
+222,205 -> 222,419
+769,815 -> 769,739
+83,147 -> 880,147
+136,148 -> 136,279
+807,241 -> 439,241
+464,240 -> 478,254
+37,839 -> 646,839
+351,316 -> 639,604
+449,492 -> 449,125
+69,892 -> 933,28
+565,161 -> 598,161
+147,802 -> 905,44
+809,861 -> 38,90
+34,80 -> 34,538
+896,405 -> 582,405
+474,201 -> 893,201
+289,64 -> 975,750
+378,785 -> 375,782
+709,472 -> 357,472
+17,14 -> 987,984
+625,46 -> 647,46
+20,84 -> 914,978
+364,811 -> 397,811
+395,726 -> 628,726
+831,89 -> 593,89
+370,562 -> 827,562
+278,371 -> 609,40
+904,529 -> 391,16
+232,829 -> 232,63
+927,121 -> 194,854
+547,280 -> 547,895
+292,904 -> 292,897
+99,525 -> 99,868
+371,44 -> 643,44
+942,74 -> 986,118
+708,179 -> 110,179
+485,637 -> 713,637
+477,512 -> 102,137
+636,657 -> 727,657
+686,564 -> 256,564
+636,169 -> 377,169
+627,943 -> 627,703
+987,795 -> 987,758
+364,827 -> 642,827
+613,694 -> 864,945
+910,521 -> 777,654
+119,394 -> 22,394
+594,439 -> 515,360
+177,11 -> 177,73
+456,628 -> 456,467
+246,214 -> 594,562
+47,790 -> 47,491
+788,21 -> 788,343
+136,847 -> 136,543
+958,302 -> 733,302
+50,981 -> 923,108
+298,179 -> 298,921
+962,644 -> 93,644
+988,671 -> 988,258
+646,140 -> 646,852
+721,264 -> 721,563
+972,407 -> 684,119
+245,422 -> 401,422
+16,494 -> 16,16
+564,72 -> 361,72
+436,390 -> 166,120
+511,571 -> 241,571
+259,215 -> 259,975
+648,841 -> 898,841
+918,881 -> 438,401
+458,561 -> 752,855
+791,192 -> 319,192
+383,929 -> 217,929
+733,26 -> 527,26
+620,160 -> 620,734
+818,181 -> 61,181
+39,21 -> 927,909
+952,208 -> 952,749
+194,55 -> 304,55
+519,673 -> 519,875
+730,919 -> 733,919
+963,269 -> 933,299
+707,112 -> 178,112
+924,349 -> 264,349
+910,94 -> 96,94
+747,289 -> 89,947
+164,956 -> 164,655
+264,300 -> 753,789
+207,672 -> 207,488
+243,838 -> 812,269
+455,320 -> 425,320
+59,964 -> 59,841
+350,373 -> 526,549
+604,683 -> 604,83
+537,281 -> 537,933
+737,634 -> 737,28
+92,909 -> 725,276
+859,335 -> 859,487
+605,495 -> 371,495
+783,155 -> 783,930
+388,591 -> 388,133
+374,634 -> 472,634
+963,914 -> 64,15
+57,435 -> 140,435
+759,619 -> 105,619
+326,501 -> 326,821
+942,136 -> 414,136
+490,376 -> 490,260
+377,59 -> 377,773
+894,169 -> 99,964
+350,511 -> 726,511
+787,728 -> 787,750
+688,11 -> 688,68
+107,514 -> 183,514
+861,12 -> 22,851
+149,49 -> 149,713
+826,737 -> 890,737
+299,307 -> 299,549
+251,648 -> 862,37
+898,85 -> 412,85
+936,168 -> 845,168
+278,677 -> 302,677
+493,878 -> 493,133
+539,205 -> 539,522
+412,495 -> 412,929
+334,605 -> 334,817
+68,462 -> 462,856
+234,134 -> 234,942
+293,823 -> 678,823
+852,874 -> 158,874
+859,612 -> 435,612
+10,876 -> 613,273
+370,13 -> 118,13
+616,774 -> 14,172
+193,543 -> 81,543
+784,179 -> 14,949
+324,533 -> 153,533
+15,976 -> 976,15
+943,52 -> 20,975
+100,34 -> 671,605
+140,552 -> 140,27
+448,497 -> 186,497
+734,355 -> 734,933
+544,131 -> 259,131
+193,84 -> 663,84
+190,949 -> 833,306
+430,34 -> 328,34
+21,46 -> 483,508
+621,202 -> 98,202
+196,874 -> 889,181
+106,217 -> 850,961
+701,891 -> 488,678
+21,597 -> 894,597
+249,21 -> 249,614
+887,808 -> 887,948
+255,711 -> 913,53
+173,447 -> 173,78
+956,224 -> 956,747
+513,882 -> 48,417
+772,591 -> 930,591
+976,98 -> 86,988
+264,67 -> 264,931
+987,982 -> 48,43
+494,514 -> 494,416
+867,785 -> 556,474
+350,902 -> 257,902
+978,977 -> 978,735
+312,240 -> 371,240
+890,112 -> 890,662
+753,327 -> 427,653
+83,888 -> 927,44
+142,480 -> 12,480
+965,39 -> 85,919
+158,926 -> 158,801
+439,22 -> 439,860
+10,26 -> 765,781
+775,838 -> 775,732
+871,607 -> 871,288
+337,850 -> 337,533
+89,581 -> 89,582
+524,977 -> 524,88
+473,283 -> 639,449
+23,324 -> 23,372
+671,486 -> 278,879
+266,98 -> 989,98
+51,947 -> 634,947
+47,18 -> 47,43
+95,239 -> 609,753
+953,34 -> 71,916
+243,685 -> 243,427
+642,537 -> 304,199
+545,41 -> 914,41
+112,860 -> 112,159
+12,12 -> 989,989
+622,907 -> 648,907
+230,983 -> 230,941
+111,868 -> 852,127
+315,895 -> 799,411
+771,533 -> 584,720
+65,492 -> 657,492
+820,315 -> 820,627
+710,554 -> 829,554
+100,967 -> 877,190
+530,733 -> 530,202
+880,28 -> 83,825
+914,448 -> 494,28
+886,344 -> 966,344
+782,923 -> 857,848
+597,632 -> 597,946
+366,789 -> 366,96
+568,834 -> 187,834
+451,687 -> 224,687
+123,12 -> 914,803
+734,42 -> 526,42
+844,116 -> 844,521
+744,976 -> 744,792
+337,837 -> 617,837
+848,139 -> 848,571
+853,264 -> 112,264
+986,965 -> 92,71
+888,892 -> 53,57
+150,342 -> 150,516
+457,264 -> 796,264
+544,595 -> 544,406
+243,118 -> 482,357
+138,804 -> 138,646
+99,80 -> 99,34
+442,883 -> 442,165
+428,72 -> 428,826
+450,815 -> 901,364
+852,516 -> 852,384
+13,969 -> 972,10
+921,50 -> 32,939
+969,470 -> 969,539
+691,238 -> 763,238
+171,733 -> 823,81
+722,963 -> 21,262
+849,203 -> 849,151
+12,99 -> 884,971
+903,240 -> 148,240
+633,140 -> 633,202
+194,393 -> 747,393
+748,43 -> 126,665
+182,155 -> 182,298
+668,814 -> 668,306
+619,384 -> 255,384
+166,341 -> 795,970
+898,870 -> 57,29
+976,148 -> 976,244
+386,525 -> 662,249
+719,67 -> 131,655
+419,847 -> 188,847
+953,823 -> 743,823
+307,299 -> 307,78
+948,253 -> 756,253
+926,938 -> 46,58
+982,618 -> 652,618
+539,742 -> 539,177
+531,974 -> 531,781
+880,922 -> 283,325
+707,257 -> 707,673
+327,308 -> 930,911
+526,170 -> 980,624
+445,653 -> 445,986
+842,737 -> 754,737
+847,982 -> 16,151
+137,426 -> 292,271
+126,556 -> 50,556
+168,766 -> 168,767
+152,46 -> 363,46
+50,381 -> 760,381
+43,943 -> 43,374
+45,964 -> 956,53
+37,403 -> 576,403
+130,317 -> 576,763
+882,840 -> 179,137
+572,608 -> 572,274
+874,977 -> 32,135
+794,56 -> 730,120
+812,841 -> 812,440
+111,66 -> 137,92
+255,287 -> 255,787
+121,137 -> 121,63
+81,811 -> 81,586
+303,365 -> 910,972
+177,134 -> 962,919
+405,41 -> 405,645
+219,934 -> 441,934
diff --git a/2021/day05/main.go b/2021/day05/main.go
new file mode 100644
index 0000000..9c0763c
--- /dev/null
+++ b/2021/day05/main.go
@@ -0,0 +1,203 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+var minX, maxX, minY, maxY int
+
+func main() {
+	maxX = h.MIN_INT
+	minX = h.MAX_INT
+	maxY = h.MIN_INT
+	minY = h.MAX_INT
+	inp := h.StdinToStringSlice()
+	lines := parseLines(inp)
+
+	fmt.Println("# Part 1")
+	findDangerSpots(filterStraight(lines))
+	fmt.Println("# Part 2")
+	findDangerSpots(lines)
+}
+
+var ventMap map[h.Coordinate]int
+
+var dangerSpots []h.Coordinate
+
+func dingMap(c h.Coordinate) {
+	s := ventMap[c]
+	s++
+	if s == 2 {
+		dangerSpots = append(dangerSpots, c)
+	}
+	ventMap[c] = s
+}
+
+func findDangerSpots(lines []Line) {
+	ventMap = make(map[h.Coordinate]int)
+	for i := range lines {
+		updateMinMax(lines[i])
+	}
+	for _, l := range lines {
+		// Find all points on this line
+		// All lines are 0 or 45 deg, so slope should always be 0,1,-1,INF,-INF
+		if l.start.X == l.end.X { // INF, -INF: vertical
+			for y := l.lowestY(); y <= l.highestY(); y++ {
+				dingMap(h.Coordinate{X: l.start.X, Y: y})
+			}
+		} else if l.start.Y == l.end.Y { //0: horizontal
+			for x := l.start.X; x <= l.end.X; x++ {
+				dingMap(h.Coordinate{Y: l.start.Y, X: x})
+			}
+		} else { // 1 or -1
+			y := l.start.Y
+			x := l.start.X
+			dingMap(h.Coordinate{Y: y, X: x})
+
+			diffY := -1
+			if l.start.Y < l.end.Y {
+				diffY = 1
+			}
+
+			for x != l.end.X && y != l.end.Y {
+				x += 1
+				y += diffY
+				dingMap(h.Coordinate{Y: y, X: x})
+			}
+		}
+	}
+	fmt.Println("Danger Spots:", len(dangerSpots))
+}
+
+type Line struct {
+	start h.Coordinate
+	end   h.Coordinate
+
+	stX float64
+	stY float64
+	edX float64
+	edY float64
+
+	slope float64
+}
+
+func (l *Line) lowestY() int {
+	if l.start.Y < l.end.Y {
+		return l.start.Y
+	}
+	return l.end.Y
+}
+
+func (l *Line) highestY() int {
+	if l.start.Y > l.end.Y {
+		return l.start.Y
+	}
+	return l.end.Y
+}
+
+func (l *Line) intersects(c h.Coordinate) bool {
+	ptX := float64(c.X)
+	ptY := float64(c.Y)
+	if (c.X == l.start.X && c.Y == l.start.Y) || (c.X == l.end.X && c.Y == l.end.Y) {
+		return true
+	}
+	if c.X < l.start.X || c.X > l.end.X {
+		return false
+	}
+	if (c.Y < l.start.Y && c.Y < l.end.Y) || (c.Y > l.start.Y && c.Y > l.end.Y) {
+		return false
+	}
+	// Check if our slope is infinite
+	if l.start.X == l.end.X {
+		if l.start.Y < l.end.Y {
+			return c.X == l.start.X && c.Y >= l.start.Y && c.Y <= l.end.Y
+		} else {
+			return c.X == l.start.X && c.Y <= l.start.Y && c.Y >= l.end.Y
+		}
+	}
+	return slope(ptX, ptY, l.stX, l.stY) == l.slope
+}
+
+func (l Line) String() string {
+	return fmt.Sprintf("%d,%d -> %d,%d; [%f]", l.start.X, l.start.Y, l.end.X, l.end.Y, l.slope)
+}
+
+func LineFromString(str string) Line {
+	start := h.Coordinate{}
+	end := h.Coordinate{}
+	r := strings.NewReader(str)
+	_, err := fmt.Fscanf(r, "%d,%d -> %d,%d", &start.X, &start.Y, &end.X, &end.Y)
+	if err != nil {
+		panic(err)
+	}
+	var l Line
+	if start.X < end.X {
+		l = Line{
+			start: start,
+			end:   end,
+		}
+	} else {
+		l = Line{
+			start: end,
+			end:   start,
+		}
+	}
+	l.stX = float64(l.start.X)
+	l.stY = float64(l.start.Y)
+	l.edX = float64(l.end.X)
+	l.edY = float64(l.end.Y)
+	l.slope = slope(l.stX, l.stY, l.edX, l.edY)
+	return l
+}
+
+func updateMinMax(line Line) {
+	if line.start.X < minX {
+		minX = line.start.X
+	}
+	if line.start.X > maxX {
+		maxX = line.start.X
+	}
+	if line.end.X < minX {
+		minX = line.end.X
+	}
+	if line.end.X > maxX {
+		maxX = line.end.X
+	}
+	if line.start.Y < minY {
+		minY = line.start.Y
+	}
+	if line.start.Y > maxY {
+		maxY = line.start.Y
+	}
+	if line.end.Y < minY {
+		minY = line.end.Y
+	}
+	if line.end.Y > maxY {
+		maxY = line.end.Y
+	}
+}
+
+func parseLines(inp []string) []Line {
+	var ret []Line
+	for i := range inp {
+		ret = append(ret, LineFromString(inp[i]))
+	}
+	return ret
+}
+
+func filterStraight(lines []Line) []Line {
+	var ret []Line
+	for i := range lines {
+		if lines[i].start.X == lines[i].end.X || lines[i].start.Y == lines[i].end.Y {
+			ret = append(ret, lines[i])
+		}
+	}
+	return ret
+}
+
+func slope(x1, y1, x2, y2 float64) float64 {
+	return (y1 - y2) / (x1 - x2)
+}
diff --git a/2021/day05/testinput b/2021/day05/testinput
new file mode 100644
index 0000000..b258f68
--- /dev/null
+++ b/2021/day05/testinput
@@ -0,0 +1,10 @@
+0,9 -> 5,9
+8,0 -> 0,8
+9,4 -> 3,4
+2,2 -> 2,1
+7,0 -> 7,4
+6,4 -> 2,0
+0,9 -> 2,9
+3,4 -> 1,4
+0,0 -> 8,8
+5,5 -> 8,2