solved 28

src/bin/problem_28.rs

@@ -0,0 +1,19 @@
+// instead of computing the spiral and summing the diagonals, only get corners
+fn main() {
+    let dimension = 1001;
+    let mut sum = 0;
+    let squares = (dimension / 2) + 1;
+    let mut last_square_end = 0;
+    for square in 0..squares {
+        if square == 0 {
+            sum = 1;
+            last_square_end = 1;
+            continue;
+        }
+        for corner in 0..4 {
+            sum += last_square_end + (square * 2) * (corner + 1);
+        }
+        last_square_end = last_square_end + (square * 2) * 4;
+    }
+    println!("{sum}");
+}