p773

Author: ian-hon

src/p773.rs

@@ -0,0 +1,70 @@
+use std::collections::HashSet;
+
+pub fn run() {
+    for i in [
+        vec![vec![1,2,3], vec![4,0,5]],
+        vec![vec![4,1,2], vec![5,0,3]],
+        vec![vec![1,2,3],vec![5,4,0]]
+    ] {
+        println!("{}", sliding_puzzle(i));
+    }
+}
+
+pub fn sliding_puzzle(board: Vec<Vec<i32>>) -> i32 {
+    if board == vec![vec![1,2,3], vec![4,5,0]] {
+        return 0;
+    }
+
+    let board: Vec<i32> = board.iter().flatten().map(|x| *x).collect();
+    let mut set: HashSet<Vec<i32>> = HashSet::new();
+    set.insert(board.clone());
+
+    let target = vec![1,2,3,4,5,0];
+    let mut nodes: Vec<Vec<i32>> = vec![board];
+    let mut count = 0;
+    loop {
+        count += 1;
+
+        let mut result: Vec<Vec<i32>> = vec![];
+        let mut flag = false;
+        for i in nodes.clone() {
+            for m in perform_all_moves(&i) {
+                if !set.insert(m.clone()) {
+                    continue;
+                }
+                if m == target {
+                    return count;
+                }
+                flag = true;
+                result.push(m);
+            }
+        }
+
+        if !flag {
+            // no changes to all nodes, means no possible moves
+            return -1;
+        }
+        nodes = result.clone();
+    }
+}
+
+pub fn perform_all_moves(n: &Vec<i32>) -> Vec<Vec<i32>> {
+    // 4 moves -> u,r,d,
+
+    let index = n.iter().position(|x| *x == 0).unwrap();
+
+    let possible_swaps = vec![
+        vec![1, 3], vec![0, 2, 4], vec![1, 5], vec![0, 4], vec![1, 3, 5], vec![2, 4]
+    ];
+
+    let mut result = vec![];
+    for s in &possible_swaps[index] {
+        let mut t = n.clone();
+        t[index] = t[*s as usize];
+        t[*s as usize] = 0;
+
+        result.push(t);
+    }
+
+    result
+}