題目：74. Search a 2D Matrix(https://leetcode.com/problems/search-a-2d-matrix/description/)

解法：

將二維陣列看成一維陣列，元素的座標可以計算出來。此解法使用二分查詢。

public class Solution {

	public boolean searchMatrix(int[][] matrix, int target) {

		int height = matrix.length;
		if(height == 0) { // in case []
			return false;
		}
		int width = matrix[0].length;
		if(width == 0) { // in case [[]]
			return false;
		}

		int from = 0;
		int to = height * width - 1;

		// loop until only two elements left
		while (to - from > 1) {
			int mid = (from + to) >> 1;
			if (matrix[mid / width][mid % width] < target) {
				from = mid;
			} else {
				to = mid;
			}
		}

		if (from == to) {
			return matrix[to / width][to % width] == target;
		} else {
			return matrix[to / width][to % width] == target || matrix[from / width][from % width] == target;
		}
	}

}