Module 14: Find Spans in the Grid

a.c

@@ -44,6 +44,7 @@ struct Span {
   int len;
   bool vert;
 };
+typedef vector<Span> Spans;  // No need for pointers, as spans are not so numerous
 
 ostream& operator<<(ostream& os, const Span& s) {
   os << "[" << s.point << " len=" << s.len << " vert=" << s.vert << "]";
@@ -171,6 +172,72 @@ struct Grid {
       return lines[0].size();
     }
   }
+  // Returns character value of the box at point 'p'
+  // 'p' must be in bounds
+  char box(const Point& p) const {
+    assert(in_bounds(p));
+    return lines[p.row][p.col];
+  }
+  // Returns true if point p is a '.' "block" in the grid
+  // 'p' must be in bounds
+  bool is_block(const Point& p) const {
+    return box(p) == '.'; 
+  }
+  bool is_blank(const Point& p) const {
+    return box(p) == '-';
+  }
+  bool is_letter(const Point& p) const {
+    char c = box(p); 
+    return c >= 'A' && c <= 'Z';
+  }
+  bool in_bounds(const Point& p) const {
+    return (p.row >= 0 && p.row < rows() && p.col >= 0 && p.col < cols());
+  }
+  // Next increments the point across the grid, one box at a time
+  // Returns true if point is still in bounds
+  bool Next(Point& p, bool vert) {
+    if (vert) {
+      p.row++;
+      if (p.row >= rows()) {
+        p.row = 0;
+        p.col++;
+      }    
+    } else {
+      p.col++;
+      if (p.col >= cols()) {
+        p.col = 0;
+        p.row++;
+      }
+    }
+    return in_bounds(p);
+  }
+  void FillSpans(bool vert) {
+    Point p;
+    // check all spans
+    while (in_bounds(p)) {
+      // for each span
+      while (in_bounds(p) && is_block(p)) {
+        Next(p, vert);
+      }
+      if (!in_bounds(p)) return;
+      Point startp = p;
+     // cout << "SPAN START: " << p << "\n";
+      
+      int len = 0;
+      do {
+        Next(p, vert);
+        len++;
+      } while (in_bounds(p) && !is_block(p));    
+      //cout << "END OF SPAN!!! len=" << len << "\n";
+      spans.push_back(Span(startp, len, vert));
+    }
+  }
+  // Add to 'spans' vector with all viable spans in the grid
+  void FillSpans() {
+    assert(spans.empty());
+    FillSpans(false);  // horiz
+    FillSpans(true);   // vert
+  }
   void LoadFromFile(string filename) {
     ifstream f;
     f.open("test");
@@ -196,8 +263,15 @@ struct Grid {
       cout << "  " << s << "\n";
     }
   }
+  void PrintSpans() const {
+    cout << "Spans:\n";
+    for (const Span& s : spans) {
+      cout << "  " << s << "\n";
+    }
+  }
   string name; // strings are initialized empty
   vector<string> lines;
+  Spans spans;
 };
 
 int main() {
@@ -208,18 +282,6 @@ int main() {
   grid.LoadFromFile("test");
   grid.Check();
   grid.Print();
-
-  Point p1;
-  Point p2(2,1);
-
-  cout << "Point1 is " << p1 << "\n";
-  cout << "Point2 is " << p2 << "\n";
-  
-  Span s1(p1, 3, true);
-  Span s2(p2, 5, false);
-
-  cout << "Span1 is " << s1 << "\n";
-  cout << "Span2 is " << s2 << "\n";
-
-  
+  grid.FillSpans();
+  grid.PrintSpans();
 }