240. Search a 2D Matrix II

Question

Write an efficient algorithm that searches for a value target in an m x n integer matrix 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.

Solution

将起始点设置为第一行的最后一列。
如果搜寻目标大于该点则向下搜索。
如果搜寻目标小于该点则向左搜索。

Code

class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        int i = 0, j = matrix[0].length - 1;
        
        while(i < matrix.length && j >= 0){
            if(matrix[i][j] == target) return true;
            else if(matrix[i][j] > target) j--;
            else i++;
        }
        return false;
    }
}