what is the number of operations for the following code?

public class NQueensBT {

public int[][] solution;

public NQueensBT(int N) {

solution = new int[N][N];

for (int i = 0; i < N; i++) {

for (int j = 0; j < N; j++) {

solution[i][j] = 0;

}

}

}

public void solve(int N) {

if(placeQueens(0, N)){

//print the result

for (int i = 0; i < N; i++) {

for (int j = 0; j < N; j++) {

System.out.print(" " + solution[i][j]);

}

System.out.println();

}

}else{

System.out.println("NO SOLUTION EXISTS");

}

}

public boolean placeQueens(int queen, int N) {

// will place the Queens one at a time, for column wise

if(queen==N){

//if we are here that means we have solved the problem

return true;

}

for (int row = 0; row < N; row++) {

// check if queen can be placed row,col

if (canPlace(solution, row, queen)) {

// place the queen

solution[row][queen] = 1;

// solve for next queen

if(placeQueens(queen+1, N)){

return true;

}

//if we are here that means above placement didn't work

//BACKTRACK

solution[row][queen]=0;

}

}

//if we are here that means we haven't found solution

return false;

}

// check if queen can be placed at matrix[row][column]

public boolean canPlace(int[][] matrix, int row, int column) {

// since we are filling one column at a time,

// we will check if no queen is placed in that particular row

for (int i = 0; i < column; i++) {

if (matrix[row][i] == 1) {

return false;

}

}

// we are filling one column at a time,so we need to check the upper and

// diagonal as well

// check upper diagonal

for (int i = row, j = column; i >= 0 && j >= 0; i--, j--) {

if (matrix[i][j] == 1) {

return false;

}

}

// check lower diagonal

for (int i = row, j = column; i < matrix.length && j >= 0; i++, j--) {

if (matrix[i][j] == 1) {

return false;

}

}

// if we are here that means we are safe to place Queen at row,column

return true;

}

public static void main(String[] args) {

int N = 10;

NQueensBT q = new NQueensBT(N);

q.solve(N);

}

}