74. Search a 2D Matrix

/**
 * @param {number[][]} matrix
 * @param {number} target
 * @return {boolean}
 */
var searchMatrix = function(matrix, target) {
  var n = matrix.length;
  var m = matrix[0].length;
  var l = 0,
    r = m * n - 1;
  while (l != r) {
    var mid = (l + r - 1) >> 1;
    if (matrix[parseInt(mid / m)][mid % m] < target) l = mid + 1;
    else r = mid;
  }
  return matrix[parseInt(r / m)][r % m] == target;
};