045

045/main.rs

@@ -0,0 +1,16 @@
+use std::collections::HashSet;
+
+fn main() {
+    let mut ps = HashSet::new();
+    let mut hs = HashSet::new();
+    let N = 500000u64;
+    for n in 1..N { hs.insert(n*(2*n-1)); }
+    for n in 1..N { ps.insert(n*(3*n -1)/2 ); }
+    for n in 286u64..N {
+        let tn = n * (n+1)/2;
+        if !hs.contains(&tn) { continue; }
+        if !ps.contains(&tn) { continue; }
+        println!("{}", tn);
+        break;
+    }
+}