Tag: programming

Question

Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

1. Each row must contain the digits 1-9 without repetition.
2. Each column must contain the digits 1-9 without repetition.
3. Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition.

Note:

• A Sudoku board (partially filled) could be valid but is not necessarily solvable.
• Only the filled cells need to be validated according to the mentioned rules.

Solution (Python)

class Solution:
    def checkRep(self, checklist):
        #print(checklist)
        for i in range(1,9+1):
            count = checklist.count(str(i))
            #print(i,count)
            if count>1:
                return False
        else:
            return True
        
    def getSquare(self,i_start,j_start,board):
        square_list = []
        for i in range(i_start,i_start+3):
            for j in range(j_start,j_start+3):
                square_list.append(board[i][j])
        return square_list
        
    def isValidSudoku(self, board: List[List[str]]) -> bool:
        # Check Rows
        for i in range(0,9):
            if self.checkRep(board[i])==False:
                return False
        
        # Check Columns
        for j in range(0,9):
            if self.checkRep([x[j] for x in board])==False:
                return False
        
        # Check Squares
        square_coords = []
        for i in range(0,3):
            for j in range(0,3):
                square_coords.append([i*3,j*3])
        #print(square_coords)
        for coord in square_coords:
            square_list = self.getSquare(coord[0],coord[1],board)
            if self.checkRep(square_list)==False:
                return False
        return True

Cracking the Coding Interview: 189 Programming Questions and Solutions

Question

Given an integer array nums, move all 0‘s to the end of it while maintaining the relative order of the non-zero elements.

Note that you must do this in-place without making a copy of the array.

Python Solution

class Solution:
    def moveZeroes(self, nums: List[int]) -> None:
        """
        Do not return anything, modify nums in-place instead.
        """
        i=0
        num_zeros = 0
        while i<len(nums):
            #print(i)
            if i<=len(nums)-num_zeros:
                if nums[i]==0:
                    nums.pop(i)
                    nums.append(0)
                    num_zeros+=1
                else:
                    i+=1
            else:
                break

Cracking the Coding Interview: 189 Programming Questions and Solutions