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;
};