Leetcode notes: Valid Sudoku

I. Title Description

Determine if a Sudoku is valid, according To:sudoku puzzles-the Rules:
Http://sudoku.com.au/TheRules.aspx.
The Sudoku board could be partially filled, where empty cells is filled with the character '.

The following figure:a partially filled Sudoku which is valid.

Two. Topic analysis

The nature of the Sudoku matrix can be summarized simply as: whether there is a unique permutation combination for each row in the matrix, each column, and each 3×3 of the nine Gongge regions 0~9 , and if the same element exists, the Sudoku matrix is illegal.

This problem is relatively simple, is to traverse all the elements of the Sudoku matrix, check whether the elements meet the nature of Sudoku. For judging whether an element is in a row, a column, or a small area, I define a keyword to hold the number of occurrences of a 0~9 number map , used as a keyword as long as the ‘1‘，‘2‘，...，‘9‘ stored object of a keyword is greater than 1, indicating that there is a duplicate in the row, column, or 3×3 nine Gongge area , traversing in this way can determine whether the matrix is legitimate.

Three. Sample code

#include <iostream>#include <vector>#include <map>using namespace STD;classsolution{ Public:BOOLIsvalidsudoku ( vector<vector<char> >& Board) { Map<char, int>Sudokumap; for(inti =0; I <9; i++) {sudokumap.clear (); for(intj =0; J <9; J + +) {sudokumap[board[i][j]]++;if((board[i][j]! ='. ') && (Sudokumap[board[i][j]] >1))return false; }        } for(inti =0; I <9; i++) {sudokumap.clear (); for(intj =0; J <9; J + +) {sudokumap[board[j][i]]++;if((board[j][i]! ='. ') && (Sudokumap[board[j][i]] >1))return false; }        } for(inti =0; I <9; i + =3)        { for(intj =0; J <9; J + =3) {sudokumap.clear (); for(intK = i; K < i +3; k++) { for(intL = j; L < J +3; l++) {sudokumap[board[k][l]]++;if((board[k][l]! ='. ') && (Sudokumap[board[k][l]] >1))return false; }                }            }        }return true; }};

The results of the operation are as follows:

1. A correct Sudoku matrix:

2. A wrong Sudoku matrix:

Four. Summary

This problem does not require the implementation of any algorithm, just design a matrix operation, use map for each row, each column or each nine in each 1~9 number of times, as long as the discovery of more than one, you can immediately negate the Sudoku, only to traverse the entire Sudoku matrix and meet the requirements, Only to be judged as valid Sudoku.

Related Topics: Sudoku solver

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Leetcode notes: Valid Sudoku