[LeetCode] 240. Search a 2D Matrix II

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.

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.

题意：给一个排序矩阵，查找一个数，如果存在则返回true，否则false；

从右上角开始找，比它大就往下，小就往左，越界就不存在

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