116 lines
2.5 KiB
Rust
116 lines
2.5 KiB
Rust
/**
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* [1706] Where Will the Ball Fall
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*/
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pub struct Solution {}
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// submission codes start here
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use std::collections::HashMap;
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const LEFT: i32 = -1;
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const RIGHT: i32 = 1;
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struct Grid {
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m: usize,
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n: usize,
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grid: Vec<Vec<i32>>,
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memory: HashMap<usize, HashMap<usize, Option<usize>>>,
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}
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impl Grid {
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fn new(grid: Vec<Vec<i32>>) -> Self {
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let m = grid.len();
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let n = grid[0].len();
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let mut memory = HashMap::new();
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// 如果可能到达m行
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// 就已经掉出去了
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let row = memory.entry(m).or_insert(HashMap::new());
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for i in 0..n {
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row.insert(i, Some(i));
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}
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Self { m, n, grid, memory }
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}
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fn search(&mut self, x: usize, y: usize) -> Option<usize> {
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if let Some(result) = self
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.memory
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.get(&x)
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.into_iter()
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.filter_map(|x| x.get(&y))
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.next()
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{
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return result.as_ref().map(|x| *x);
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}
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let result = if self.grid[x][y] == LEFT {
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// 挡板朝向左边
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if y > 0 {
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if self.grid[x][y - 1] == RIGHT {
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None
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} else {
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self.search(x + 1, y - 1)
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}
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} else {
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None
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}
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} else {
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// 挡板朝向右边
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if y < self.n - 1 {
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if self.grid[x][y + 1] == LEFT {
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None
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} else {
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self.search(x + 1, y + 1)
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}
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} else {
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None
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}
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};
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let row = self.memory.entry(x).or_insert(HashMap::new());
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row.insert(y, result.clone());
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result
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}
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}
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impl Solution {
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pub fn find_ball(grid: Vec<Vec<i32>>) -> Vec<i32> {
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let mut grid = Grid::new(grid);
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let mut result = Vec::with_capacity(grid.n);
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for i in 0..grid.n {
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result.push(if let Some(pos) = grid.search(0, i) {
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pos as i32
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} else {
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-1
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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_1706() {
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assert_eq!(
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vec![1, -1, -1, -1, -1],
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Solution::find_ball(vec![
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vec![1, 1, 1, -1, -1],
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vec![1, 1, 1, -1, -1],
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vec![-1, -1, -1, 1, 1],
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vec![1, 1, 1, 1, -1],
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vec![-1, -1, -1, -1, -1]
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])
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);
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}
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}
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