1 files changed, 157 insertions, 12 deletions

diff --git a/src/main.zig b/src/main.zig
index 56c15fe..38799a8 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1,4 +1,5 @@
 const std = @import("std");
+const ArrayList = std.ArrayList;
 const print = std.debug.warn;
 
 fn p1() void {
@@ -239,14 +240,6 @@ fn p9() void {
     }
 }
 
-//fn sum(array: []usize) usize {
-//    var counter: usize = 0;
-//    for (array) |i| {
-//        counter += i;
-//    }
-//    return counter;
-//}
-
 fn p10() void {
     const size: usize = 2_000_001;
     var primes: [size]bool = undefined;
@@ -274,19 +267,170 @@ fn p10() void {
     print("{}\n", .{sum});
 }
 
+fn strtoint(str: []u8) usize {
+    var sum: usize = 0;
+    var str_len: usize = len(str);
+
+    for (str) |c, j| {
+        sum += (str[str_len - (j + 1)] - 48) * (exp(10, j));
+    }
+
+    return sum;
+}
+
+fn exp(x: usize, y: usize) usize {
+    var i: usize = 0;
+    var total: usize = 1;
+    while (i < y) : (i += 1) {
+        total *= x;
+    }
+    return total;
+}
+
 fn p11() void {
     var array: [20][20]usize = undefined;
 
+    var i: usize = 0;
+    var j: usize = 0;
+    var k: usize = 0;
+
     if (std.fs.cwd().openFile("p11", .{ .read = true })) |file| {
         var str: [4096]u8 = undefined;
-        if (file.read(&str)) |val| {
-            print("{}", .{str[0]});
+        if (file.read(&str)) |str_len| {
+            while (i < str_len) : (i += 3) {
+                array[j][k] = strtoint(str[i .. i + 2]);
+                if (j == 19) {
+                    j = 0;
+                    k += 1;
+                } else {
+                    j += 1;
+                }
+            }
         } else |err| {
             print("{}\n", .{err});
         }
     } else |err| {
         print("{}\n", .{err});
     }
+
+    var largest: usize = 0;
+    var product: usize = 0;
+    i = 0;
+    while (i < 16) : (i += 1) {
+        j = 0;
+        while (j < 16) : (j += 1) {
+            product = array[i][j] * array[i + 1][j] * array[i + 2][j] * array[i + 3][j];
+            if (product > largest) {
+                largest = product;
+            }
+            product = array[i][j] * array[i][j + 1] * array[i][j + 2] * array[i][j + 3];
+            if (product > largest) {
+                largest = product;
+            }
+            product = array[i][j] * array[i + 1][j + 1] * array[i + 2][j + 2] * array[i + 3][j + 3];
+            if (product > largest) {
+                largest = product;
+            }
+            product = array[i + 3][j] * array[i + 2][j + 1] * array[i + 1][j + 2] * array[i][j + 3];
+            if (product > largest) {
+                largest = product;
+            }
+        }
+    }
+    print("{}\n", .{largest});
+}
+
+fn gen_primes() ArrayList(usize) {
+    var bool_primes = ArrayList(bool).init(std.heap.page_allocator);
+    const size: usize = 10_000_000;
+    var i: usize = 0;
+    while (i < size) : (i += 1) {
+        if (bool_primes.append(true)) |val| {} else |err| {
+            print("{}", .{"allocation error"});
+        }
+    }
+
+    i = 2;
+    while (i < size) : (i += 1) {
+        if (bool_primes.items[i]) {
+            var j: usize = 2;
+            while (j * i < size) : (j += 1) {
+                bool_primes.items[j * i] = false;
+            }
+        }
+    }
+
+    i = 2;
+    var primes = ArrayList(usize).init(std.heap.page_allocator);
+    while (i < size) : (i += 1) {
+        if (bool_primes.items[i]) {
+            if (primes.append(i)) |val| {} else |err| {
+                print("{}", .{"allocation error"});
+            }
+        }
+    }
+
+    bool_primes.deinit();
+
+    return primes;
+}
+
+const Prime = struct { n: usize, count: usize };
+const my_primes_size = 10;
+
+fn p12() void {
+    var i: usize = 1;
+    var triangle: usize = 0;
+    var largest: usize = 0;
+
+    var primes = gen_primes();
+
+    while (i < 20000) : (i += 1) {
+        triangle += i;
+        var my_primes: [my_primes_size]Prime = undefined;
+        var count: usize = 0;
+
+        var j: usize = 0;
+        while (j < my_primes_size) : (j += 1) {
+            my_primes[j].count = 0;
+        }
+
+        j = 0;
+        while (j < primes.items.len) : (j += 1) {
+            if (triangle % primes.items[j] == 0) {
+                var prime: Prime = .{ .n = primes.items[j], .count = 0 };
+                my_primes[count] = prime;
+                count += 1;
+            } else if (primes.items[j] > triangle) {
+                break;
+            }
+        }
+
+        var t: usize = triangle;
+        while (t != 1) {
+            j = 0;
+            while (j < count) : (j += 1) {
+                if (t % my_primes[j].n == 0) {
+                    t /= my_primes[j].n;
+                    my_primes[j].count += 1;
+                }
+            }
+        }
+
+        j = 0;
+        var divisor_amount: usize = 1;
+        while (j < my_primes_size) : (j += 1) {
+            if (my_primes[j].count == 0) {
+                break;
+            }
+            divisor_amount *= my_primes[j].count + 1;
+        }
+
+        if (divisor_amount > 500) {
+            print("{},{}\n", .{ triangle, divisor_amount });
+            break;
+        }
+    }
 }
 
 pub fn main() !void {
@@ -297,8 +441,9 @@ pub fn main() !void {
     //p5();
     //p6();
     //p7();
-    p8();
-    p9();
+    //p8();
+    //p9();
     //p10();
     //p11();
+    p12();
 }