N queen problem C ++ non-recursive solutionOne

operation result:

 

code show as below:

1 #include <bits / stdc ++. H>
 2  using  namespace std;
 3 #include <bits / stdc ++. H>
 4  using  namespace std;
 5  const  int MAX = 1024 ;
 6  const  char * LINE32 = " ------ -------------------------- " ;
 7  const  bool PRINT_DETAILS = false ; 
 8  long  long n, cnt = 0 ;     // n is the number of queens , Cnt represents the number of solutions 
9  int queen [MAX + 1];
10 
11 void print() {
12     cout << LINE32 << endl;
13     cout << "第" << cnt << "个解法: " << endl;
14     for (int i = 1; i <= n; i++) {
15         if (i != 1) {
16             cout << ", ";
17         }
18         cout << "(" << i << "," << queen[i] << ")";
19     } 
20     cout << endl;
21     for (int i = 1; i <= n; i++) {
22         for (int j = 1; j <= n; j++) {
23             if (queen[i] != j) {
24                 cout << 'x';
25             } else {
26                 cout << 'Q';
27             }
 28          }
 29          cout << endl;
 30      }
 31  }
 32  
33  bool check ( int row, int col) {     // Check whether the queen can be placed at the (row, col) coordinate 
34      for ( int placed = 1 ; placed < row; placed ++ ) {
 35          if (queen [placed] == col || abs (row-placed) == abs (col- queen [placed])) {
 36              return  false ;
 37          }
 38      }
 39      return  true;
 40  }
 41  void solve ( int n) {
 42      int row = 1 ;     // row indicates the row currently being placed, the initial value is 1, indicates that the
      queen is placed from the first row 43 queen [row] = 1 ;         // That is, a [1] = 1 means that at the beginning, put a queen in (1, 1) 
44      while (row> 0 ) {     // row value is finally 0, because when all conditions are checked, the first row Backtracking upwards, the row value is 0 
45          if (row> n) {
 46              // Find a solution, and then need to backtrack upwards: check from the next column of the previous line 
47              cnt ++ ;
 48              if (PRINT_DETAILS) {
 49                 print ();
 50              } 
 51              queen [-row] ++ ; 
 52          } else  if (queen [row]> n) {
 53              // queen [row] indicates the position of the column to be detected on the current row 
 54              // At this point, all positions of the row row have been checked, and the same upward traceback: check from the next column of the previous row 
55              queen [-row] ++ ; 
 56          } else  if (check (row, queen [row] )) {
 57              // Find a matching position, start to place the next row, starting from the first column 
58              queen [++ row] = 1 ; 
 59          } else {
 60             // This time indicates that this position does not match, check the position of the next column in this row 
61              queen [row] ++ ; 
 62          } 
 63      } 
 64  } 
 65  
66  int main () {
 67      // input 
68      cout << " Enter the queen Number: " ; 
 69      cin >> n;
 70      // compute 
71      clock_t begin = clock (); 
 72      solve (n); 
 73      clock_t end = clock (); 
 74      // output 
75      cout << LINE32 <<endl;
 76      cout << n << " Queen's problem in all " << cnt << " kinds of solutions " << endl; 
 77      cout << LINE32 << endl;
 78      cout << " Non-recursive solution 1 solution " < <n << " Queen's Question Time-consuming " << / * end-begin << "Dotted" << * / ( double ) (end-begin) / CLOCKS_PER_SEC << " s " << endl;
 79      return  0 ;
80 } 
81 // 14 9~11s

 

Compared with recursive solution 1:

①The operation of recursive solution 1:

②The operation of non-recursive solution 1:

You can see, non-recursive solution 1 run slightly more than 1 time a number of recursive solution, which is not in line with expectations , logically speaking, non-recursive solution running time should be shorter next blog post will compare non-recursive and recursive solution 2 Solution 2 .