moonlightshadow123
6/21/2017 - 1:48 PM

240. Search a 2D Matrix II

  1. Search a 2D Matrix II
class Solution(object):
    def searchMatrix(self, mat, target):
        """
        :type mat: List[List[int]]
        :type target: int
        :rtype: bool
        """
        if len(mat) == 0 or len(mat[0]) == 0:
            return False
        rowNum = len(mat)
        colNum = len(mat[0])
        rowIndex = 0
        colIndex = colNum - 1
        while colIndex >= 0 and rowIndex <= rowNum - 1:
            # Like previous `Search a 2D Matrix` problem,
            # except that the while loop will go for many times rather than just 1 or 2 times.
            if mat[rowIndex][colIndex] < target:
                rowIndex += 1
            elif mat[rowIndex][colIndex] > target:
                colIndex -= 1
            else:
                return True
        return False

https://leetcode.com/problems/search-a-2d-matrix-ii/#/description

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.