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 in ascending from left to right.
- Integers in each column are sorted in ascending from top to bottom.
For example,
Consider the following matrix:
[ [1, 4, 7, 11, 15], [2, 5, 8, 12, 19], [3, 6, 9, 16, 22], [10, 13, 14, 17, 24], [18, 21, 23, 26, 30] ]
Given target = 5, return true.
Given target = 20, return false.
1 public class Solution { 2 public boolean searchMatrix(int[][] matrix, int target) { 3 if(matrix.length == 0 || matrix[0].length == 0) return false; 4 int i = 0,j = matrix[0].length-1; 5 while(i < matrix.length && j >= 0){ 6 if(matrix[i][j] == target) return true; 7 if(matrix[i][j] < target) i++; 8 else j--; 9 } 10 return false; 11 } 12 }
该题矩阵比较特殊，可以从右上角X开始比较， 如果target > X,则到下一行，如果target < X,则要往回走一列。题目在编程之美里面出现过。
解法2： 该题也可以使用二分法进行查找。
参考代码：http://www.cnblogs.com/Dylan-Java-NYC/p/4881258.html