N-Queens II LeetCode solution in Java

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class Solution {
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  int count = 0;
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  public int totalNQueens(int n) {
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    boolean col[] = new boolean[n];
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    boolean diag[] = new boolean[2 * n - 1];
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    boolean rdiag[] = new boolean[2 * n - 1];
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    countSolution(n, col, diag, rdiag, 0);
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    return count;
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  }
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  void countSolution(int n, boolean[] col, boolean[] diag, boolean[] rdiag, int r) {
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    if (r == n) {
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      count++;
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      return;
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    }
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    for (int c = 0; c < n; c++) {
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      if (col[c] == false && diag[r + c] == false && rdiag[r - c + n - 1] == false) {
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        col[c] = true;
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        diag[r + c] = true;
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        rdiag[r - c + n - 1] = true;
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        countSolution(n, col, diag, rdiag, r + 1);
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        col[c] = false;
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        diag[r + c] = false;
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        rdiag[r - c + n - 1] = false;
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      }
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    }
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  }
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}