Homework New

Exercise/Homework2/Q3.rs

@@ -1,39 +1,79 @@
-use std::io;
+use std::io::{self, BufRead};
 
-pub struct Status{
-    pos: i32,
-    a: char, // from
-    b: char, // to
-    c: char  // aux
+
+fn next(s: &Vec<char>, start: usize, end: usize) -> Vec<usize> {
+    let n = end - start;
+    let mut nxt = vec![0; n];
+    let mut j = 0;
+    for i in 1..n {
+        while j > 0 && s[start + i] != s[start + j] {
+            j = nxt[j - 1];
+        }
+        if s[start + i] == s[start + j] {
+            j += 1;
+        }
+        nxt[i] = j;
+    }
+    nxt
 }
 
-
 fn main(){
-    let mut s = String::new();
-    io::stdin().read_line(&mut s).unwrap();
-    let n: i32 = s.trim().parse().unwrap();
+let stdin = io::stdin();
+for line in stdin.lock().lines() {
+    let s = line.unwrap();
+    if s.trim().is_empty() { continue; }
 
-    let mut stack: Vec<Status> = Vec::new();
-    stack.push(Status{pos: n, a: 'A', b: 'C', c: 'B'});
-    let mut max = 0;
+    let c: Vec<char> = s.trim().chars().collect();
+    let n = c.len();
+    let mut nxt = next(&c, 0, c.len());
+    let mut plen = -1;
 
-    let mut output = String::new(); //输出，要不然太慢总会超时
-
-    while !stack.is_empty() {
-        if stack.len() > max {
-            max = stack.len();
+    //计算P的话可以直接用最长后缀算，使用KMP
+    for len in (1..n).rev() {
+        let mode: Vec<char> = c[n - len..n].to_vec();
+        let tmp: Vec<usize> = next(&mode, 0, mode.len());
+        let mut i = 0;
+        let mut j = 0;
+        while i < n - 1 {
+            while j > 0 && c[i] != mode[j] {
+                j = tmp[j - 1];
+            }
+            if c[i] == mode[j] {
+                j += 1;
+            }
+            if j == mode.len() {
+                plen = mode.len() as i32;
+                break;
+            }
+            if plen > 0 {
+                break;
+            }
+            i += 1;
         }
-
-        let mut end = stack.pop().unwrap();
-        if end.pos == 1 {
-            output.push_str(&format!("Move disk from {} to {}\n", end.a, end.b));
-        } else {
-            stack.push(Status{pos: end.pos - 1, a: end.c, b: end.b, c: end.a});
-            stack.push(Status{pos: 1, a: end.a, b: end.b, c: end.c});
-            stack.push(Status{pos: end.pos - 1, a: end.a, b: end.c, c: end.b});
-
+        if plen > 0 {
+            break;
         }
     }
-    print!("{}", output);
-    println!("{}", max);
+
+    //计算Q，用len1和len2，如果2 * qlen > len(s)，则len(Q) = 0
+
+    let mut qlen = 0;
+    if nxt[n - 1] > 0 {
+        qlen = nxt[nxt[n - 1] - 1];
+    }
+    if 2 * qlen > n {
+        qlen = 0;
+    } else {
+        qlen = n - 2 * qlen;
+    }
+
+    if plen < 0 {
+        plen = 0;
+    }
+    let out = qlen as i32 + plen as i32;
+    println!("{}", out);
+
+    //println!("qlen: {}", qlen);
+    //println!("plen: {}", plen);
+}
 }