A slightly working flood iterator and a working compass iterator.

matrix.hpp

@@ -1,11 +1,18 @@
 #pragma once
 #include <vector>
+#include <queue>
 #include <string>
+#include <array>
+#include <fmt/core.h>
+#include "point.hpp"
+
+using fmt::println;
 
 namespace matrix {
+  using std::vector, std::queue, std::array;
 
-  typedef std::vector<int> Row;
-  typedef std::vector<Row> Matrix;
+  typedef vector<int> Row;
+  typedef vector<Row> Matrix;
 
   struct each_cell {
     size_t x = ~0;
@@ -42,6 +49,18 @@ namespace matrix {
     void dump();
   };
 
+  struct compass {
+    size_t x = 0; // these are set in constructor
+    size_t y = 0; // again, no fancy ~ trick needed
+    array<int, 4> x_dirs{0, 1, 0, -1};
+    array<int, 4> y_dirs{-1, 0, 1, 0};
+    size_t max_dirs=0;
+    size_t dir = ~0;
+
+    compass(Matrix &mat, size_t x, size_t y);
+    bool next();
+  };
+
   /*
    * Just a quick thing to reset a matrix to a value.
    */
@@ -51,5 +70,28 @@ namespace matrix {
     }
   }
 
+  inline bool inbounds(Matrix &mat, size_t x, size_t y) {
+    // since Point.x and Point.y are size_t any negatives are massive
+    bool res = (y < mat.size()) && (x < mat[0].size());
+    return res;
+  }
+
   void dump(const std::string &msg, Matrix &map, int show_x=-1, int show_y=-1);
+
+  struct flood {
+    Matrix &mat;
+    Point start;
+    int old_val;
+    int new_val;
+    queue<Point> q;
+    Point current_loc;
+    int x;
+    int y;
+    matrix::compass dirs;
+
+    flood(Matrix &mat, Point start, int old_val, int new_val);
+    bool next();
+    bool next_working();
+  };
+
 }