[LeetCode]Search a 2D Matrix

Question :

• 　　

  Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:

   

  • Integers in each row are sorted from left to right.
  • The first integer of each row is greater than the last integer of the previous row.

   

  For example,

  Consider the following matrix:

  [
    [1,   3,  5,  7],
    [10, 11, 16, 20],
    [23, 30, 34, 50]
  ]
  

  Given target = 3, return true.

• Idea : 
  　　把matrix視為一維陣列處理。
• Code:
  

  bool searchMatrix(int** matrix, int matrixRowSize, int matrixColSize, int target) {
      
      int low = 0, high=matrixRowSize*matrixColSize-1;
      int mid;
      while(low <= high) {
          mid = low + (high - low )/2; // avoid to buffer overflow.
      
          if(matrix[mid/matrixColSize][mid%matrixColSize] < target)
              low = mid + 1; 
          else if(matrix[mid/matrixColSize][mid%matrixColSize] > target)
              high = mid -1;
          else
              return true;
      }
      return false;
  }