63 lines
1.5 KiB
Rust
63 lines
1.5 KiB
Rust
/**
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* [688] Knight Probability in Chessboard
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*/
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pub struct Solution {}
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// submission codes start here
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const DIRECTIONS: [(i32, i32); 8] = [
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(-1, -2),
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(1, -2),
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(-1, 2),
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(1, 2),
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(-2, -1),
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(2, -1),
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(-2, 1),
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(2, 1),
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];
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impl Solution {
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pub fn knight_probability(n: i32, k: i32, row: i32, column: i32) -> f64 {
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let (n, k) = (n as usize, k as usize);
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let (row, column) = (row as usize, column as usize);
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let mut dp = vec![vec![vec![0f64; n]; n]; k + 1];
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for step in 0..=k {
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for x in 0..n {
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for y in 0..n {
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if step == 0 {
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dp[step][x][y] = 1f64;
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} else {
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for &(dx, dy) in DIRECTIONS.iter() {
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let nx = x as i32 + dx;
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let ny = y as i32 + dy;
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if nx >= 0 && nx < n as i32 && ny >= 0 && ny < n as i32 {
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let (nx, ny) = (nx as usize, ny as usize);
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dp[step][x][y] += dp[step - 1][nx][ny] / 8f64;
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}
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}
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}
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}
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}
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}
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dp[k][row][column]
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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_688() {
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assert_eq!(0.0625, Solution::knight_probability(3, 2, 0, 0));
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assert_eq!(1.0, Solution::knight_probability(1, 0, 0, 0));
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}
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}
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