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# hw2 - Spring 2009 CS 32 Homework 2 Time due 9:00 PM Tuesday...

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Spring 2009 CS 32 Homework 2 Time due: 9:00 PM Tuesday, April 28 Write a C++ function named pathExists that determines whether or not a there's a path from start to finish in a 10x10 maze. Here is the prototype: bool pathExists(char maze[][10], int sr, int sc, int er, int ec); // Return true if there is a path from (sr,sc) to (er,ec) // through the maze; return false otherwise The parameters are A 2-dimensional 10x10 character array of Xs and dots that represents the maze. Each 'X' represents a wall, and each '.' represents a walkway. The starting coordinates in the maze: sr, sc; the row number and column number range from 0 to 9. The ending coordinates in the maze: er, ec; the row number and column number range from 0 to 9. The function must determine if there is a path from maze[sr][sc] to maze[er][ec] that includes only walkways, no walls. The path may turn only north, east, south, and west, but not diagonally. You must use a stack data structure. Your solution will use the following simple class, which represents an (r,c) coordinate pair: class Coord { public: Coord(int rr, int cc) : m_r(rr), m_c(cc) {} int r() const { return m_r; } int c() const { return m_c; } private: int m_r; int m_c; }; (Our convention is that (0,0) is the northwest (upper left) corner, with south (down) being the increasing r direction and east (right) being the increasing c direction.) The stack you must use is a stack of Coords. You may either write your own stack class, or use the stack class in the C+ + Standard Library (pp. 309-311 in the textbook discuss that class). Here's an example of the relevant functions in the library's stack class: #include <stack> using namespace std; int main() { stack<Coord> coordStack; // declare a stack of Coords Coord a(5,6); coordStack.push(a); // push the coordinate (5,6) coordStack.push(Coord(3,4)); // push the coordinate (3,4) ... Coord b = coordStack.top(); // look at top item in the stack coordStack.pop(); // remove the top item from stack if (coordStack.empty()) // Is the stack empty? cout << "empty!" << endl; cout << coordStack.size() << endl; // num of elements } Here is pseudocode for your function: Push the starting coordinate onto the coordinate stack. While the stack is not empty, { Pop the top coordinate off the stack. This gives you the current (r,c) location that your algorithm is exploring.

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hw2 - Spring 2009 CS 32 Homework 2 Time due 9:00 PM Tuesday...

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