[Leetcode 59, Medium] Speral Matrix II

Problem:

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

For example,
Given n = 3,

You should return the following matrix:

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

Analysis:

Solutions:

C++:

    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int> > matrix(n, vector<int>(n, 0));
        if(n == 0)
            return matrix;

        int search_bound = n / 2;
        int next_number = 1;
        for(int start = 0; start < search_bound; ++start) {
            for(int index = start; index < n - 1 - start; ++index)
                matrix[start][index] = next_number++;
                
            for(int index = start; index < n - 1 - start; ++index)
                matrix[index][n - 1 - start] = next_number++;
                
            for(int index = n - 1 - start; index > start; --index)
                matrix[n - 1 - start][index] = next_number++;
                
            for(int index = n - 1 - start; index > start; --index)
                matrix[index][start] = next_number++;
        }
        
        if(n % 2 == 1)
            matrix[search_bound][search_bound] = next_number;

        return matrix;
    }

Java :

Python: