82 lines
1.7 KiB
C++
82 lines
1.7 KiB
C++
/* Code contributed by Devang Shah to MakeContributions/DSA GitHub repository
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Below CPlusPlus code displays all possible solutions for a N-Queens problem.
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Problem: Given a N x N chess board, arrange N queens in a way such that no two queens attack each other. Two queens are attacking each other if they are in same row, same column or diagonal
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Input: N
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Output: All solutions ( in grid format {Q - Queen, * - empty cell} ) of the N-queens problem
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Time Complexity: O(N!)
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*/
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#include <iostream>
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using namespace std;
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int a[30];
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int place(int pos)
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{
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int i;
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for (i = 1; i < pos; i++)
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{
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if ((a[i] == a[pos]) || ((abs(a[i] - a[pos]) == abs(i - pos))))
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return 0;
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}
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return 1;
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}
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void print_sol(int n)
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{
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int i, j;
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for (i = 1; i <= n; i++)
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{
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for (j = 1; j <= n; j++)
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{
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if (a[i] == j)
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cout << "Q\t";
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else
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cout << "*\t";
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}
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cout << "\n";
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}
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}
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void queen(int n)
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{
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int k = 1;
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a[k] = 0;
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int count = 0;
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while (k != 0)
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{
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a[k] = a[k] + 1;
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while ((a[k] <= n) && !place(k))
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a[k]++;
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if (a[k] <= n)
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{
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if (k == n)
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{
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count++;
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cout << "Solution #" << count << "\n";
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print_sol(n);
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}
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else
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{
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k++;
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a[k] = 0;
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}
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}
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else
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k--;
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}
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cout << "\nTotal solutions=" << count;
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}
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int main()
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{
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unsigned int n;
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cin >> n;
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if (n < 15)
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queen(n);
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else
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cout << "Invalid input. Program crashed";
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return 0;
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}
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