diff --git a/CMakeLists.txt b/CMakeLists.txt
index a95f9bd..fbb04a5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3,5 +3,5 @@ project(aoc_2021 C)
 
 set(CMAKE_C_STANDARD 99)
 
-add_executable(aoc_2021 src/main.c src/day_1.c src/day.h src/day_2.c src/puzzle_input.c src/puzzle_input.h src/day_3.c src/day_4.c)
+add_executable(aoc_2021 src/main.c src/day_1.c src/day.h src/day_2.c src/puzzle_input.c src/puzzle_input.h src/day_3.c src/day_4.c src/day_5.c)
 target_link_libraries(aoc_2021 m)
diff --git a/inputs/day_5.txt b/inputs/day_5.txt
new file mode 100644
index 0000000..0f41bb1
--- /dev/null
+++ b/inputs/day_5.txt
@@ -0,0 +1,500 @@
+527,299 -> 430,299
+828,228 -> 81,228
+40,126 -> 842,928
+30,390 -> 30,741
+196,853 -> 196,599
+388,795 -> 388,300
+326,398 -> 326,766
+63,865 -> 63,407
+119,453 -> 282,453
+478,396 -> 824,396
+934,189 -> 612,189
+739,122 -> 306,555
+394,970 -> 394,249
+213,693 -> 213,336
+955,11 -> 688,11
+632,211 -> 818,211
+324,662 -> 66,404
+652,773 -> 811,614
+964,746 -> 402,184
+105,959 -> 850,214
+454,852 -> 594,852
+685,669 -> 124,669
+95,11 -> 873,789
+737,266 -> 484,266
+547,701 -> 764,484
+290,20 -> 290,164
+103,870 -> 283,870
+762,582 -> 762,431
+69,154 -> 55,154
+584,37 -> 308,37
+200,218 -> 200,336
+50,871 -> 766,155
+256,212 -> 919,875
+421,779 -> 959,241
+987,42 -> 304,725
+139,791 -> 330,600
+728,53 -> 845,53
+807,907 -> 423,907
+765,642 -> 868,642
+701,279 -> 701,75
+29,890 -> 542,890
+929,105 -> 59,975
+23,355 -> 485,817
+597,440 -> 454,440
+770,338 -> 629,338
+856,203 -> 856,858
+262,806 -> 951,806
+976,879 -> 976,179
+91,879 -> 950,20
+378,216 -> 378,440
+300,794 -> 507,794
+174,890 -> 907,157
+850,37 -> 171,37
+61,375 -> 117,375
+350,984 -> 460,984
+454,361 -> 672,361
+118,802 -> 118,448
+225,929 -> 974,180
+880,69 -> 341,608
+52,986 -> 891,147
+367,529 -> 367,707
+302,385 -> 674,385
+970,122 -> 145,947
+526,676 -> 214,364
+463,651 -> 463,708
+861,779 -> 168,86
+11,965 -> 913,63
+461,63 -> 944,63
+610,532 -> 199,121
+715,594 -> 512,594
+107,94 -> 490,94
+913,558 -> 404,558
+25,55 -> 911,941
+861,443 -> 861,329
+411,113 -> 884,113
+125,636 -> 740,636
+55,157 -> 815,917
+901,744 -> 547,744
+86,340 -> 86,866
+64,698 -> 270,698
+519,324 -> 371,324
+857,634 -> 857,35
+384,137 -> 28,137
+859,981 -> 859,302
+351,757 -> 351,204
+460,557 -> 460,792
+954,581 -> 112,581
+303,405 -> 303,599
+445,588 -> 246,588
+664,114 -> 664,107
+556,397 -> 556,714
+210,112 -> 939,841
+477,953 -> 180,656
+913,536 -> 913,333
+405,152 -> 552,152
+805,848 -> 805,12
+759,318 -> 759,163
+443,167 -> 231,167
+906,336 -> 906,122
+470,781 -> 546,705
+536,359 -> 814,81
+445,167 -> 935,167
+226,729 -> 730,729
+940,876 -> 510,446
+433,87 -> 533,87
+437,887 -> 186,887
+609,217 -> 431,217
+766,388 -> 663,388
+397,826 -> 82,826
+411,324 -> 411,437
+632,75 -> 632,290
+583,646 -> 836,899
+118,703 -> 118,307
+907,275 -> 721,275
+321,191 -> 321,362
+168,594 -> 168,55
+857,290 -> 284,290
+879,232 -> 879,456
+578,206 -> 28,756
+47,144 -> 47,777
+815,521 -> 445,151
+765,680 -> 523,438
+139,817 -> 534,422
+372,539 -> 36,539
+900,758 -> 900,987
+248,835 -> 558,835
+259,774 -> 472,774
+375,436 -> 172,436
+265,754 -> 265,556
+753,161 -> 753,307
+677,648 -> 677,743
+79,427 -> 79,34
+391,304 -> 754,304
+339,275 -> 339,548
+596,584 -> 596,684
+677,656 -> 64,43
+789,409 -> 814,434
+420,436 -> 822,436
+842,552 -> 181,552
+931,124 -> 69,986
+976,147 -> 97,147
+854,673 -> 400,219
+622,300 -> 622,339
+331,503 -> 331,585
+450,795 -> 489,756
+47,883 -> 920,10
+387,843 -> 793,843
+87,452 -> 583,948
+84,77 -> 610,603
+145,147 -> 903,147
+203,971 -> 203,67
+797,171 -> 713,171
+472,559 -> 872,959
+116,349 -> 116,43
+82,654 -> 461,275
+208,641 -> 208,25
+212,474 -> 198,488
+521,396 -> 187,396
+56,916 -> 937,916
+359,806 -> 888,806
+841,220 -> 841,857
+288,791 -> 288,610
+254,584 -> 254,37
+302,485 -> 743,926
+414,590 -> 510,686
+899,600 -> 132,600
+923,543 -> 93,543
+597,103 -> 918,103
+130,143 -> 920,933
+741,216 -> 867,216
+915,852 -> 723,852
+519,842 -> 541,842
+197,407 -> 197,526
+214,775 -> 214,728
+854,345 -> 938,345
+719,820 -> 788,751
+46,937 -> 758,225
+685,173 -> 685,354
+192,500 -> 500,500
+947,663 -> 335,51
+810,675 -> 209,74
+329,753 -> 62,753
+651,866 -> 614,866
+760,627 -> 258,627
+491,645 -> 491,473
+988,17 -> 22,983
+921,951 -> 14,44
+176,591 -> 176,750
+401,129 -> 381,129
+145,329 -> 145,905
+286,116 -> 273,103
+91,185 -> 91,756
+634,752 -> 634,14
+252,645 -> 290,645
+954,645 -> 954,350
+115,177 -> 115,121
+52,682 -> 52,51
+638,966 -> 841,763
+851,854 -> 152,155
+77,433 -> 599,955
+309,964 -> 309,426
+413,958 -> 413,235
+150,831 -> 150,118
+981,383 -> 422,942
+748,776 -> 748,631
+509,127 -> 509,231
+595,136 -> 301,136
+458,838 -> 458,912
+608,290 -> 239,290
+57,921 -> 946,32
+524,756 -> 317,963
+567,425 -> 567,443
+832,716 -> 740,716
+182,218 -> 650,686
+421,936 -> 127,642
+342,366 -> 441,267
+672,754 -> 376,754
+758,724 -> 758,379
+602,795 -> 349,795
+409,887 -> 988,308
+508,13 -> 561,66
+582,946 -> 369,733
+332,542 -> 136,346
+295,256 -> 926,256
+839,846 -> 839,698
+649,333 -> 522,333
+837,625 -> 837,184
+64,85 -> 618,639
+210,930 -> 414,930
+428,651 -> 214,651
+832,362 -> 832,926
+92,385 -> 92,799
+132,978 -> 747,978
+545,867 -> 545,947
+256,708 -> 239,725
+830,962 -> 570,962
+356,150 -> 781,575
+116,29 -> 965,878
+342,546 -> 53,835
+576,170 -> 780,170
+40,767 -> 656,151
+417,514 -> 417,114
+60,517 -> 60,137
+715,760 -> 557,760
+508,329 -> 508,371
+467,427 -> 19,427
+227,531 -> 742,16
+332,450 -> 867,450
+274,323 -> 524,323
+539,677 -> 460,677
+224,403 -> 224,845
+373,916 -> 366,916
+400,84 -> 400,895
+824,502 -> 824,804
+835,967 -> 347,479
+838,639 -> 838,798
+386,247 -> 616,17
+165,445 -> 408,445
+941,849 -> 913,849
+792,469 -> 792,600
+630,521 -> 630,344
+338,418 -> 298,458
+163,571 -> 527,571
+102,290 -> 911,290
+213,745 -> 213,267
+225,795 -> 778,242
+986,988 -> 10,12
+239,445 -> 239,829
+526,714 -> 526,225
+224,774 -> 953,45
+467,915 -> 467,291
+395,148 -> 204,339
+871,549 -> 392,549
+817,452 -> 939,330
+942,19 -> 942,937
+166,627 -> 207,627
+901,306 -> 901,158
+103,339 -> 466,339
+351,19 -> 815,19
+677,659 -> 203,185
+270,25 -> 46,25
+318,461 -> 318,129
+283,428 -> 884,428
+696,966 -> 893,966
+388,237 -> 381,230
+172,978 -> 172,18
+434,499 -> 156,777
+630,682 -> 501,682
+272,340 -> 251,361
+410,94 -> 410,885
+863,920 -> 747,920
+986,985 -> 14,13
+369,626 -> 256,513
+638,496 -> 571,496
+196,609 -> 638,609
+710,959 -> 454,959
+642,578 -> 642,468
+457,720 -> 379,798
+88,86 -> 88,320
+361,352 -> 157,556
+55,57 -> 450,57
+532,204 -> 532,750
+76,856 -> 658,274
+818,750 -> 397,329
+829,801 -> 128,100
+843,892 -> 433,892
+516,438 -> 516,59
+216,534 -> 216,914
+767,973 -> 56,973
+288,91 -> 342,91
+51,52 -> 417,418
+979,570 -> 497,570
+438,471 -> 579,330
+751,57 -> 751,619
+199,403 -> 118,403
+811,903 -> 251,343
+294,47 -> 950,703
+457,107 -> 967,617
+976,42 -> 34,984
+84,194 -> 265,194
+944,341 -> 131,341
+935,398 -> 276,398
+716,135 -> 513,135
+846,690 -> 846,950
+786,858 -> 786,960
+491,677 -> 491,57
+283,781 -> 15,513
+51,736 -> 557,230
+503,825 -> 928,825
+70,980 -> 960,90
+947,135 -> 732,350
+968,873 -> 336,241
+955,185 -> 157,983
+887,644 -> 887,530
+315,315 -> 604,604
+728,163 -> 728,67
+759,286 -> 759,55
+255,73 -> 653,471
+156,942 -> 983,115
+840,877 -> 69,106
+828,451 -> 828,117
+742,655 -> 349,655
+576,664 -> 576,427
+74,960 -> 962,72
+293,169 -> 711,169
+151,771 -> 929,771
+860,908 -> 427,475
+169,466 -> 279,356
+557,25 -> 24,25
+500,93 -> 108,93
+332,119 -> 463,119
+24,385 -> 739,385
+527,866 -> 985,866
+212,781 -> 595,398
+548,774 -> 730,774
+774,514 -> 30,514
+627,45 -> 627,885
+73,932 -> 984,21
+95,616 -> 811,616
+464,401 -> 458,401
+774,442 -> 534,202
+407,422 -> 407,211
+444,86 -> 444,358
+184,541 -> 184,325
+679,97 -> 841,259
+235,895 -> 571,895
+454,517 -> 121,517
+487,243 -> 564,243
+216,237 -> 953,974
+202,136 -> 202,536
+117,848 -> 762,203
+676,557 -> 89,557
+940,456 -> 940,548
+931,426 -> 899,426
+31,398 -> 145,398
+211,537 -> 589,159
+853,977 -> 673,977
+713,863 -> 216,366
+311,814 -> 335,814
+330,879 -> 127,879
+897,585 -> 185,585
+503,64 -> 677,64
+623,886 -> 254,517
+795,989 -> 795,516
+508,712 -> 904,316
+964,892 -> 101,29
+797,38 -> 797,901
+911,10 -> 632,10
+646,831 -> 284,831
+424,187 -> 957,720
+365,751 -> 538,578
+821,840 -> 38,57
+868,799 -> 242,799
+343,181 -> 555,393
+280,880 -> 280,795
+419,294 -> 419,79
+595,545 -> 595,775
+285,516 -> 285,816
+137,933 -> 137,61
+278,245 -> 610,577
+282,142 -> 21,142
+723,720 -> 251,248
+552,461 -> 654,461
+833,546 -> 785,546
+503,129 -> 450,76
+455,436 -> 653,436
+236,132 -> 926,822
+559,754 -> 559,615
+262,169 -> 275,169
+942,551 -> 942,273
+178,709 -> 178,69
+11,476 -> 811,476
+238,664 -> 238,867
+121,514 -> 278,514
+348,300 -> 348,453
+981,905 -> 981,139
+870,71 -> 870,69
+12,693 -> 931,693
+438,676 -> 110,348
+167,436 -> 167,839
+419,146 -> 170,146
+231,183 -> 231,278
+766,967 -> 700,967
+834,624 -> 445,624
+392,639 -> 392,808
+739,176 -> 161,176
+186,126 -> 186,451
+675,709 -> 675,629
+613,483 -> 981,483
+495,21 -> 581,107
+626,234 -> 111,234
+28,291 -> 28,883
+65,932 -> 942,55
+988,977 -> 54,43
+108,523 -> 108,820
+936,893 -> 211,168
+51,935 -> 957,29
+949,892 -> 108,51
+478,32 -> 228,32
+473,107 -> 82,498
+449,401 -> 449,645
+833,110 -> 295,648
+982,138 -> 982,111
+438,447 -> 661,224
+208,745 -> 917,36
+287,934 -> 832,389
+974,17 -> 974,105
+391,251 -> 517,377
+57,256 -> 57,704
+580,217 -> 626,171
+468,383 -> 348,383
+185,127 -> 185,851
+633,878 -> 20,265
+659,85 -> 659,698
+64,828 -> 64,592
+216,812 -> 287,812
+707,396 -> 707,167
+173,54 -> 173,723
+467,963 -> 936,963
+61,123 -> 371,433
+794,52 -> 794,595
+604,653 -> 244,293
+352,840 -> 90,840
+354,383 -> 788,383
+770,280 -> 770,621
+494,486 -> 897,486
+126,252 -> 361,252
+97,618 -> 491,224
+945,262 -> 945,72
+138,495 -> 138,107
+767,561 -> 304,561
+59,981 -> 841,199
+902,846 -> 499,846
+883,22 -> 128,22
+699,173 -> 840,32
+889,22 -> 113,798
+647,896 -> 647,226
+221,928 -> 221,66
+633,145 -> 648,130
+91,935 -> 91,162
+87,36 -> 983,932
+882,916 -> 638,916
+942,72 -> 38,976
+159,401 -> 123,437
+762,452 -> 762,721
+228,515 -> 130,613
+751,353 -> 387,717
+256,449 -> 256,811
+176,866 -> 176,778
+894,985 -> 894,462
+831,708 -> 148,25
+140,920 -> 574,920
+639,873 -> 585,873
+791,716 -> 224,149
+117,691 -> 117,158
+825,689 -> 873,641
+656,191 -> 134,191
+862,818 -> 78,34
+22,952 -> 961,13
+982,555 -> 982,21
\ No newline at end of file
diff --git a/src/day.h b/src/day.h
index 7b7769f..7be662a 100644
--- a/src/day.h
+++ b/src/day.h
@@ -5,5 +5,6 @@ int day_1();
 int day_2();
 int day_3();
 int day_4();
+int day_5();
 
 #endif //AOC_2021_DAY_H
diff --git a/src/day_5.c b/src/day_5.c
new file mode 100644
index 0000000..c0ccdc3
--- /dev/null
+++ b/src/day_5.c
@@ -0,0 +1,138 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "puzzle_input.h"
+#include "day.h"
+
+//#define DEBUG
+
+#define MAX_VENT_LINES 1000
+#define GRID_SIZE 1000
+
+typedef struct {
+    int64_t start_x;
+    int64_t start_y;
+    int64_t end_x;
+    int64_t end_y;
+} range_t;
+
+parse_ret_t parse_vent_line(char * buffer, void * data, uint16_t index) {
+    range_t * range_data = (range_t *)data;
+    range_t *range = &range_data[index];
+    parse_ret_t res;
+
+    char * start = strtok(buffer, " -> ");
+    char * end = strtok(NULL, " -> ");
+
+    res = parse_long(strtok(start, ","), &range->start_x, 10);
+
+    if (res != PARSER_OK) {
+        return res;
+    }
+
+    res = parse_long(strtok(NULL, ","), &range->start_y, 10);
+
+    if (res != PARSER_OK) {
+        return res;
+    }
+
+    res = parse_long(strtok(end, ","), &range->end_x, 10);
+
+    if (res != PARSER_OK) {
+        return res;
+    }
+
+    res = parse_long(strtok(NULL, ","), &range->end_y, 10);
+
+    if (res != PARSER_OK) {
+        return res;
+    }
+
+    return PARSER_OK;
+}
+
+int day_5() {
+    range_t data[MAX_VENT_LINES];
+    uint16_t len;
+    uint8_t part1_grid[GRID_SIZE][GRID_SIZE] = {0};
+    uint8_t part2_grid[GRID_SIZE][GRID_SIZE] = {0};
+
+    parse_ret_t res = read_input_single_line("../inputs/day_5.txt", (void *)data, MAX_VENT_LINES, parse_vent_line, &len);
+
+    if (res != PARSER_OK) {
+        printf("Error parsing input: %d", res);
+        return -1;
+    }
+
+    for (int line_ndx = 0; line_ndx < len; line_ndx++) {
+        range_t * line = &data[line_ndx];
+        int x = (int)line->start_x;
+        int y = (int)line->start_y;
+
+        int x_done = 0;
+        int y_done = 0;
+        while (!x_done || !y_done) {
+            if (line->start_x == line->end_x || line->start_y == line->end_y) {
+                part1_grid[x][y]++;
+            }
+
+            part2_grid[x][y]++;
+            if (x == line->end_x) {
+                x_done = 1;
+            }
+            else {
+                if (line->start_x < line->end_x) {
+                    x++;
+                }
+                else {
+                    x--;
+                }
+            }
+
+            if (y == line->end_y) {
+                y_done = 1;
+            }
+            else {
+                if (line->start_y < line->end_y) {
+                    y++;
+                }
+                else {
+                    y--;
+                }
+            }
+        }
+    }
+
+    uint16_t danger_points_p1 = 0;
+    uint16_t danger_points_p2 = 0;
+    for (int x = 0; x < GRID_SIZE; x++) {
+        for (int y = 0; y < GRID_SIZE; y++) {
+#ifdef DEBUG
+
+            if (part2_grid[y][x] == 0) {
+                printf(".");
+            }
+            else {
+                printf("%d", part2_grid[y][x]);
+            }
+#endif
+
+            if (part1_grid[x][y] >= 2) {
+                danger_points_p1++;
+            }
+
+            if (part2_grid[x][y] >= 2) {
+                danger_points_p2++;
+            }
+        }
+#ifdef DEBUG
+        printf("\n");
+#endif
+    }
+
+    printf("PART 1: There are %d danger zones\n", danger_points_p1);
+    printf("PART 2: There are %d danger zones\n", danger_points_p2);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/src/main.c b/src/main.c
index 8200fdd..ab43528 100644
--- a/src/main.c
+++ b/src/main.c
@@ -28,6 +28,9 @@ int main(int argc, char * argv[]) {
         case 4:
             day_4();
             break;
+        case 5:
+            day_5();
+            break;
         default:
             printf("Invalid day ding dong!\n");
             return -2;
diff --git a/src/puzzle_input.c b/src/puzzle_input.c
index cfe536e..2c16cf7 100644
--- a/src/puzzle_input.c
+++ b/src/puzzle_input.c
@@ -73,6 +73,8 @@ parse_ret_t read_input_single_line(const char * file_path, void * data, uint16_t
                 }
 
                 buffer_ndx = 0;
+
+                memset(buffer, 0, BUFFER_SIZE);
             }
             else {
                 buffer[buffer_ndx] = (char)c;