LeetCode Algorithm 0059 - Spiral Matrix II (Medium)

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Problem Link: https://leetcode.com/problems/spiral-matrix-ii/

Related Topics: Array

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Description

Given a positive integer n , generate a square matrix filled with elements from $1$1 to $n^2$n2 in spiral order.

Example:

Input: 3
Output:
[
 [ 1, 2, 3 ],
 [ 8, 9, 4 ],
 [ 7, 6, 5 ]
]

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Solution C++

// Author: https://blog.csdn.net/DarkRabbit
// Problem: https://leetcode.com/problems/spiral-matrix-ii/
// Difficulty: Medium
// Related Topics: `Array`

#pragma once

#include "pch.h"

namespace P59SpiralMatrixII
{
    class Solution
    {
        public:
        vector<vector<int>> generateMatrix(int n)
        {
            if (n < 1)
            {
                return vector<vector<int>>();
            }

            vector<vector<int>> matrix = vector<vector<int>>(n, vector<int>(n, 0));

            int val = 1;
            int startRow = 0;
            int startCol = 0;
            int endRow = n - 1;
            int endCol = n - 1;

            while (startRow <= endRow && startCol <= endCol)
            {
                for (int c = startCol; c <= endCol; c++)
                {
                    matrix[startRow][c] = val++;
                }
                startRow++;

                for (int r = startRow; r <= endRow; r++)
                {
                    matrix[r][endCol] = val++;
                }
                endCol--;

                for (int c = endCol; c >= startCol; c--)
                {
                    matrix[endRow][c] = val++;
                }
                endRow--;

                for (int r = endRow; r >= startRow; r--)
                {
                    matrix[r][startCol] = val++;
                }
                startCol++;
            }

            return matrix;
        }
    };
}

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