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  2. Check if Every Row and Column Contains All Numbers

Arrays

Check if Every Row and Column Contains All Numbers

Problem Description

An n x n matrix is valid if every row and every column contains all the integers from 1 to n (inclusive).

Given an n x n integer matrix matrix, return true if the matrix is valid. Otherwise, return false.

Constraints:

  • n == matrix.length == matrix[i].length
  • 1 <= n <= 100
  • 1 <= matrix[i][j] <= n

https://leetcode.com/problems/check-if-every-row-and-column-contains-all-numbers/

Examples

Example 1
Input: matrix = [[1,2,3],[3,1,2],[2,3,1]]
Output: true
Example 2
Input: matrix = [[1,1,1],[1,2,3],[1,2,3]]
Output: false

How to Solve

The problem is about n x n matrix and 1 to n (inclusive) values. Using a set data structure, check the cell value of each row and column doesn’t appear more than once.

The solution uses a set for horizontal and array of sets for vertical. When a row is scanned, it checks the horizontal set. When all rows are scanned, it checks the array of vertical sets. If all are length n, return True.

Solution

  • class CheckIfEveryRowAndColumnContainsAllNumbers {
    public:
        bool checkValid(vector<vector<int>>& matrix) {
            int n = matrix.size();
            // check rows
            for (int r = 0; r < n; ++r) {
                vector<int> counts(n + 1, 0);
                for (int c = 0; c < n; ++c) {
                    if (counts[matrix[r][c]] > 0) { return false; }
                    counts[matrix[r][c]]++;
                }
            }
            // check cols
            for (int c = 0; c < n; ++c) {
                vector<int> counts(n + 1, 0);
                for (int r = 0; r < n; ++r) {
                    if (counts[matrix[r][c]] > 0) { return false; }
                    counts[matrix[r][c]]++;
                }
            }
            return true;
        }
    };
    
  • class CheckIfEveryRowAndColumnContainsAllNumbers {
        public boolean checkValid(int[][] matrix) {
            int n = matrix.length;
            // check rows
            for (int r = 0; r < n; ++r) {
                int[] counts = new int[n + 1];
                for (int c = 0; c < n; ++c) {
                    if (counts[matrix[r][c]] > 0) { return false; }
                    counts[matrix[r][c]]++;
                }
            }
            // check cols
            for (int c = 0; c < n; ++c) {
                int[] counts = new int[n + 1];
                for (int r = 0; r < n; ++r) {
                    if (counts[matrix[r][c]] > 0) { return false; }
                    counts[matrix[r][c]]++;
                }
            }
            return true;
        }
    }
    
  • /**
     * @param {number[][]} matrix
     * @return {boolean}
     */
    var checkValid = function(matrix) {
        const n = matrix.length;
        // check rows
        for (let r = 0; r < n; r++) {
            let counts = new Array(n + 1);
            counts.fill(0);
            for (let c = 0; c < n; c++) {
                if (counts[matrix[r][c]] > 0) { return false; }
                counts[matrix[r][c]]++;
            }
        }
        //check cols
        for (let c = 0; c < n; c++) {
            let counts = new Array(n + 1);
            counts.fill(0);
            for (let r = 0; r < n; r++) {
                if (counts[matrix[r][c]] > 0) { return false; }
                counts[matrix[r][c]]++;
            }
        }
        return true;
    };
    
  • class CheckIfEveryRowAndColumnContainsAllNumbers:
        def checkValid(self, matrix: List[List[int]]) -> bool:
            n = len(matrix)
            # check rows
            for r in range(n):
                counts = [0 for _ in range(n + 1)]
                for c in range(n):
                    if counts[matrix[r][c]] > 0:
                        return False
                    counts[matrix[r][c]] += 1
            # check cols
            for c in range(n):
                counts = [0 for _ in range(n + 1)]
                for r in range(n):
                    if counts[matrix[r][c]] > 0:
                        return False
                    counts[matrix[r][c]] += 1
            return True
    
  • # @param {Integer[][]} matrix
    # @return {Boolean}
    def check_valid(matrix)
        n = matrix.size
        # check rows
        (0...n).each do |r|
            counts = Array.new(n + 1, 0)
            (0...n).each do |c|
                if counts[matrix[r][c]] > 0
                    return false
                end
                counts[matrix[r][c]] += 1
            end
        end
        # check cols
        (0...n).each do |c|
            counts = Array.new(n + 1, 0)
            (0...n).each do |r|
                if counts[matrix[r][c]] > 0
                    return false
                end
                counts[matrix[r][c]] += 1
            end
        end
        return true
    end
    

Complexities

  • Time: O(n^2)
  • Space: O(n^2)
Easy
Matrix
Array