Leetcode 54 - spiral matrix - Using directions - 2015 June

SpiralMatrix_UsingDirections_2015June.cpp

 /*
 Julia chose the blog to study Leetcode 54: Spiral matrix on June 11, 2015. 
 http://gongxuns.blogspot.ca/2012/12/leetcode-spiral-matrix.html 
 */
  vector<int> spiralOrder(vector<vector<int> > &matrix) {
      vector<int> result;
      int row = matrix.size();
      if(row == 0) return result;
      int col = matrix[0].size();
      if(col == 0) return result;
  
      //define the step for 4 directions
      int x[4] = { 1, 0, -1, 0 };
      int y[4] = { 0, 1, 0, -1 };
 
     int visitedRows = 0;
     int visitedCols = 0;
 
     // define direction: 0 means up, 1 means down, 2 means left, 3 means up
     int direction = 0;
     int startx = 0, starty = 0;
     int candidateNum = 0, moveStep = 0;
     
     while (true)
     {
         if (x[direction] == 0) // visit y axis
          candidateNum = row - visitedRows;
         else // visit x axis
          candidateNum = col - visitedCols;
         
         if (candidateNum <= 0)  
         break;
         
         result.push_back(matrix[starty][startx]);
         
         moveStep++;
         
         if (candidateNum == moveStep) // change direction            
         {
             visitedRows += x[direction] == 0 ? 0 : 1;
             visitedCols += y[direction] == 0 ? 0 : 1;
             direction = (direction + 1) % 4;
             moveStep = 0;
         }
         
         startx += x[direction];
         starty += y[direction];
     }
     
     return result;
 }