240. Search a 2D Matrix II

JIAKAOBO

LeetCode

感谢赞助!

• ㊗️
• 大家
• offer
• 多多！

Problem

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.

Code

class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        int row = 0;
        int col = matrix[0].length - 1;

        while(col >= 0 && row < matrix.length) {
            int num = matrix[row][col];
            if(num == target) return true;

            if(num > target) {
                col--;
            } else {
                row++;
            }
        }

        return false;
    }
}

class Solution:
    def searchMatrix(self, matrix, target):
        """
        :type matrix: List[List[int]]
        :type target: int
        :rtype: bool
        """

        if not matrix or matrix and not matrix[0]:
            return False

        # 从右上角搜索
        row = 0
        col = len(matrix[0]) - 1

        while col >= 0 and row <= len(matrix) - 1:
            num = matrix[row][col]
            if target == num:
                return False
            elif target < num:
                col-= 1
            else:
                row += 1

        return False