037 ok

037/main.rs

@@ -0,0 +1,64 @@
+use std::collections::HashSet;
+
+fn er() -> HashSet<u32> {
+    let mut nums = Vec::new();
+    let size = 1_000_000;
+    for n in 0..size+1 { nums.push(true); }
+    let mut p = 1;
+    while true {
+        let mut found = false;
+        for i in p+1..size {
+            if nums[i] {
+                found = true;
+                p = i;
+                break;
+            }
+        }
+        if !found { break; }
+        for i in (2 * p .. size).step_by(p) {
+            nums[i] = false;
+        }
+    }
+    let mut res = HashSet::new();
+    for i in 2..size {
+        if nums[i] { res.insert(i as u32); }
+    }
+    return res;
+}
+
+fn trl(n: u32) -> u32 {
+    let s = n.to_string();
+    let mut chars = s.chars();
+    let f = chars.next().unwrap();
+    //chars.next_back();
+    let mut res = String::from(chars.as_str());
+    res.parse::<u32>().unwrap()
+}
+
+fn test(p: u32, hs: &HashSet<u32>) -> bool {
+    let mut tl = p;
+    while tl > 10 {
+        if !hs.contains(&tl) { return false; }
+        tl = trl(tl);
+    }
+    if !hs.contains(&tl) { return false; }
+    let mut tr = p;
+    while tr > 0 {
+        if !hs.contains(&tr) { return false; }
+        tr /= 10;
+    }
+    return true;
+}
+
+fn main() {
+    let hs = er();
+    let mut sum = 0;
+    for p in hs.iter() {
+        if *p < 10 { continue; }
+        if test(*p, &hs) {
+            println!("{}", p);
+            sum += p;
+        }
+    }
+    println!("sum: {}", sum);
+}