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.

这道题很简单就不多说了，就是通过每一行的首数字大小先判断在哪一行，然后在某一行里搜索。其实如果高效的话应该在每一行里还做二分搜索，我就犯懒了。。反正也过了

public class Search2DMatrix {
	public static void main(String args[]){
		Search2DMatrix sm = new Search2DMatrix();
		int[][] put = {{1,   3,  5,  7},
				  {10, 11, 16, 20},
				  {23, 30, 34, 50}};
		System.out.println(sm.searchMatrix(put, 12));
	}
	public boolean searchMatrix(int[][] matrix, int target) {
		int i=0;
		while(i<matrix.length-1){
			if(target>=matrix[i][0]&&target<matrix[i+1][0]){
				for(int j=0;j<matrix[i].length;j++)
					if(matrix[i][j]==target)	return true;
			}
			i++;
		}
		for(int j=0;j<matrix[matrix.length-1].length;j++){
			if(matrix[matrix.length-1][j]==target)	return true;
		}
		return false;
		}
}

【Leetcode】Search a 2D Matrix in JAVA