add: day4

apollod4.py

@@ -0,0 +1,48 @@
+with open("src/bin/d4p2_custom.txt", "r") as inputFile:
+    lines = inputFile.read().split("\n")
+
+# part 1
+
+horiz, verts = 0, 0
+cols = [""]*len(lines)
+for i, row in enumerate(lines):
+    horiz += row.count("XMAS") + row.count("SAMX")
+    for j, c in enumerate(row):
+        cols[j] += c
+
+for col in cols:
+    verts += col.count("XMAS") + col.count("SAMX")
+
+diags = 0
+for lineIndex, line in enumerate(lines):
+    if lineIndex > len(lines)-4:
+        break
+    for colIndex in range(len(line) - 3):
+        if lines[lineIndex][colIndex] in "SX":
+            downRight = "".join(lines[lineIndex+n][colIndex+n] for n in range(4))
+            if downRight in {"XMAS", "SAMX"}:
+                diags += 1
+    for colIndex in range(3, len(line)):
+        if lines[lineIndex][colIndex] in "SX":
+            downLeft = "".join(lines[lineIndex+n][colIndex-n] for n in range(4))
+            if downLeft in {"XMAS", "SAMX"}:
+                diags += 1
+
+print(horiz + verts + diags)
+
+# part 2
+xmases = 0
+for rowIndex, line in enumerate(lines):
+    for colIndex, c in enumerate(line):
+        if c == "A":
+            try:
+                surrounds = lines[rowIndex-1][colIndex-1] + \
+                            lines[rowIndex-1][colIndex+1] + \
+                            lines[rowIndex+1][colIndex-1] + \
+                            lines[rowIndex+1][colIndex+1]
+                if surrounds in {"SSMM", "MMSS", "MSMS", "SMSM"}:
+                    xmases += 1
+            except IndexError:
+                pass
+
+print(xmases)

src/bin/d4p2.rs

@@ -10,7 +10,6 @@ fn solve(lines: Vec<String>) -> SResult<usize> {
         grid.push(line);
     }
     let mut total = 0;
-    let word: Vec<char> = "XMAS".chars().collect();
     for x in 0..grid.len() {
         for y in 0..grid[x].len() {
             if grid[x][y] != 'A' {

src/bin/d4p2_custom.txt

@@ -0,0 +1,3 @@
+ A 
+M M
+S S

src/lib.rs

@@ -25,7 +25,7 @@ pub type Pair<T = usize> = (T, T);
 pub fn next((x, y): Pair, (xvel, yvel): Pair<i64>, width: usize) -> Option<Pair> {
     let x = x as i64 + xvel;
     let y = y as i64 + yvel;
-    if x < 0 || y < 0 || x == width as i64 || y == width as i64 {
+    if x < 0 || y < 0 || x >= width as i64 || y >= width as i64 {
         None
     } else {
         Some((x as usize, y as usize))