LC_Magic_Grid.java

class Solution {
    public int numMagicSquaresInside(int[][] grid) {
        
        int ans=0;
        int m=grid.length;
        int n= grid[0].length;
        for(int row=0; row+2<m ; row++){
            for(int col=0; col+2<n ; col++){
                if(isMagicSquare(grid,row,col)){
                    ans++;
                }
            }
        }
        return ans;
    }
    
    private boolean isMagicSquare( int[][] grid, int row, int col){
        boolean[] seen= new boolean[10];
        for (int i=0; i<3; i++){
            for(int j=0; j<3; j++){
                int num= grid[row +i][col+j];
                if(num<1 || num>9) return false;
                if(seen[num]) return false;
                seen[num]= true;
            }
        }
        
        // check if diagonal sums are same value
        int diagonal1 =
            grid[row][col] + grid[row + 1][col + 1] + grid[row + 2][col + 2];
        int diagonal2 =
            grid[row + 2][col] + grid[row + 1][col + 1] + grid[row][col + 2];

        if (diagonal1 != diagonal2) return false;

        // check if all row sums share the same value as the diagonal sums
        int row1 = grid[row][col] + grid[row][col + 1] + grid[row][col + 2];
        int row2 =
            grid[row + 1][col] +
            grid[row + 1][col + 1] +
            grid[row + 1][col + 2];
        int row3 =
            grid[row + 2][col] +
            grid[row + 2][col + 1] +
            grid[row + 2][col + 2];

        if (!(row1 == diagonal1 && row2 == diagonal1 && row3 == diagonal1)) {
            return false;
        }

        // check if all column sums share same value as the diagonal sums
        int col1 = grid[row][col] + grid[row + 1][col] + grid[row + 2][col];
        int col2 =
            grid[row][col + 1] +
            grid[row + 1][col + 1] +
            grid[row + 2][col + 1];
        int col3 =
            grid[row][col + 2] +
            grid[row + 1][col + 2] +
            grid[row + 2][col + 2];

        if (!(col1 == diagonal1 && col2 == diagonal1 && col3 == diagonal2)) {
            return false;
        }

        return true;
    }
}