Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly
Sign up
Appearance settings

Commit 7af65c8

Browse files
Add implementation for the N-Queens problem using backtracking
1 parent b0c7c09 commit 7af65c8

File tree

1 file changed

+112
-0
lines changed

1 file changed

+112
-0
lines changed

‎Backtracking/nQueensProblem.java

Lines changed: 112 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,112 @@
1+
public class nQueensProblem {
2+
public static void main(String[] args) {
3+
int n = 4;
4+
char[][] board = new char[n][n];
5+
6+
for (int i = 0; i < n; i++) {
7+
for (int j = 0; j < n; j++) {
8+
board[i][j] = 'X';
9+
}
10+
11+
}
12+
13+
nqueen(board, 0);
14+
}
15+
16+
static void nqueen(char[][] board, int row) {
17+
int n = board.length;
18+
19+
// base case
20+
if (n == row) {
21+
for (int i = 0; i < n; i++) {
22+
for (int j = 0; j < n; j++) {
23+
System.out.print(board[i][j]);
24+
}
25+
System.out.println();
26+
}
27+
System.out.println();
28+
return;
29+
}
30+
31+
for (int j = 0; j < n; j++) {
32+
33+
if (isSafe(board, row, j)) {
34+
board[row][j] = 'Q';
35+
nqueen(board, row + 1); // resursive callll
36+
board[row][j] = 'X';
37+
38+
}
39+
}
40+
41+
}
42+
43+
static boolean isSafe(char[][] board, int row, int col) {
44+
45+
int n = board.length;
46+
47+
// check row
48+
for (int j = 0; j < n; j++) {
49+
if (board[row][j] == 'Q') {
50+
return false;
51+
}
52+
}
53+
54+
// check coloum
55+
for (int i = 0; i < n; i++) {
56+
if (board[i][col] == 'Q') { // neds to change [i][col]
57+
return false;
58+
}
59+
}
60+
61+
// check right top diagonal
62+
int i = row;
63+
int j = col;
64+
65+
while (i >= 0 && j < n) {
66+
if (board[i][j] == 'Q')
67+
return false;
68+
69+
i--;
70+
j++;
71+
}
72+
73+
// check the right buttom diagonal
74+
i = row;
75+
j = col;
76+
77+
while (i < n && j < n) {
78+
if (board[i][j] == 'Q')
79+
return false;
80+
81+
i++;
82+
j++;
83+
}
84+
85+
// check the left buttom diagonal
86+
87+
i = row;
88+
j = col;
89+
90+
while (i < n && j >= 0) {
91+
if (board[i][j] == 'Q')
92+
return false;
93+
94+
i++;
95+
j--;
96+
}
97+
98+
// check the left top diaonal
99+
i = row;
100+
j = col;
101+
102+
while (i >= 0 && j >= 0) {
103+
if (board[i][j] == 'Q')
104+
return false;
105+
106+
i--;
107+
j--;
108+
}
109+
110+
return true;
111+
}
112+
}

0 commit comments

Comments
(0)

AltStyle によって変換されたページ (->オリジナル) /