1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
|
#include "csapp.h"
#define CONFLICT 0
#define NO_CONFLICT 1
static int ndselect(int n) {
for (int column = 0; column < n; column++) {
int pid = fork();
if (pid == 0) {
return column;
}
waitpid(pid, NULL, 0);
}
/* TODO: A loop is missing here that spawns processes and waits for them! */
exit(0);
}
static int conflict(int x1, int y1, int x2, int y2) {
return x1 == x2
|| y1 == y2
|| x1 + y1 == x2 + y2
|| x1 - y1 == x2 - y2;
}
static bool check_conflict(int size, int board[size], int column) {
for (int i = 0; i < column; i++) {
if (conflict(board[i], i, board[column], column) == 1) return CONFLICT;
}
return NO_CONFLICT;
}
static void print_line_sep(int size) {
for (int i = 0; i < size; ++i)
printf("+---");
printf("+\n");
}
static void print_board(int size, int board[size]) {
for (int i = 0; i < size; ++i) {
print_line_sep(size);
for (int j = 0; j < size; ++j)
printf("|%s", board[i] == j ? " ♕ " : " ");
printf("|\n");
}
print_line_sep(size);
printf("\n");
}
int main(int argc, char **argv) {
if (argc != 2)
app_error("Usage: %s [SIZE]", argv[0]);
int size = atoi(argv[1]);
if (size < 3 || size > 9)
app_error("Give board size in range from 4 to 9!");
int board[size];
/* TODO: A loop is missing here that initializes recursive algorithm. */
for (int row = 0; row < size; row++) {
int column = ndselect(size);
board[row] = column;
if (check_conflict(size, board, row) == CONFLICT)
exit(0);
}
print_board(size, board);
return 0;
}
|
