class Solution {
    public int[][] generateMatrix(int n) {
        int[][] result = new int[n][n];
        int num = 1;
        for(int i = 0; i < n/2; i++){
            for(int j = i; j < n-1-i; j++){//上
                result[i][j] = num++;
            }
            for (int j = i; j < n-1-i; j++){ //右
                result[j][n-1-i] = num++;
            }
            for(int j = n-1-i; j > i; j--){ //下
                result[n-1-i][j] = num++;
            }
            for(int j = n-1-i; j > i; j--){
                result[j][i] = num++;
            }
        }
        if(n % 2 == 1){
            result[n/2][n/2] = num;
        }
        return result;
    }
}