90 lines
2.3 KiB
Rust
90 lines
2.3 KiB
Rust
/**
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* [52] N-Queens II
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*
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* The n-queens puzzle is the problem of placing n queens on an n x n chessboard such that no two queens attack each other.
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* Given an integer n, return the number of distinct solutions to the n-queens puzzle.
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*
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* <strong class="example">Example 1:
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* <img alt="" src="https://assets.leetcode.com/uploads/2020/11/13/queens.jpg" style="width: 600px; height: 268px;" />
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* Input: n = 4
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* Output: 2
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* Explanation: There are two distinct solutions to the 4-queens puzzle as shown.
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*
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* <strong class="example">Example 2:
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*
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* Input: n = 1
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* Output: 1
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*
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*
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* Constraints:
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*
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* 1 <= n <= 9
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*
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*/
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pub struct Solution {}
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// problem: https://leetcode.cn/problems/n-queens-ii/
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// discuss: https://leetcode.cn/problems/n-queens-ii/discuss/?currentPage=1&orderBy=most_votes&query=
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// submission codes start here
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use std::collections::VecDeque;
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impl Solution {
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pub fn total_n_queens(n: i32) -> i32 {
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let n = n as usize;
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let mut result = 0;
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let mut stack = VecDeque::new();
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for i in 0..n {
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stack.push_back((0usize, i, false));
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}
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let mut x_occupied = vec![false; n];
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let mut y_occupied = vec![false; 2 * n - 1];
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let mut z_occupied = vec![false; 2 * n - 1];
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while let Some((x, y, flag)) = stack.pop_back() {
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if flag {
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x_occupied[y] = false;
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y_occupied[n - 1 + x - y] = false;
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z_occupied[x + y] = false;
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} else {
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x_occupied[y] = true;
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y_occupied[n - 1 + x - y] = true;
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z_occupied[x + y] = true;
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stack.push_back((x, y, true));
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if x == n - 1 {
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result += 1;
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continue;
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}
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for j in 0..n {
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// 注意这里在判断的点是(x + 1, j)
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if !x_occupied[j] && !y_occupied[n + x - j] && !z_occupied[x + 1 + j] {
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stack.push_back((x + 1, j, false));
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}
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}
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}
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}
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result
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}
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}
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// submission codes end
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_52() {
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assert_eq!(1, Solution::total_n_queens(1));
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assert_eq!(2, Solution::total_n_queens(4));
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assert_eq!(14200, Solution::total_n_queens(12));
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}
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}
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