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.
思路：
这道题非常有技巧，我们选择右上角的那个点，然后进行比较，如果大，则向下走，如果小则向右。（因为从那个点开始，下面永远大于，左边永远小于）
class Solution {
public boolean searchMatrix(int[][] matrix, int target) {
if(matrix.length ==0) return false;
if(matrix[0].length ==0) return false;
int row =0;
int col = matrix[0].length -1;
while(row<matrix.length && col >=0){
if(matrix[row][col] == target){
return true;
}
if(matrix[row][col] > target){
col --;
}
else if(matrix[row][col] < target){
row++;
}
}
return false;
}
}
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