Strange unique prime triplets: Difference between revisions

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@@ Line 118: / Line 118: @@
     std::vector<bool> sieve(limit, true);
     if (limit > 0)
+        sieve[0] = false;
+    if (limit > 1)
         sieve[1] = false;
-    for (size_t i = 0; i < limit; i += 2)
+    for (size_t i = 4; i < limit; i += 2)
         sieve[i] = false;
     for (size_t p = 3; ; p += 2) {
@@ Line 401: / Line 403: @@
 : prime_sieve ( n -- )
   here over erase
+notprime!
 notprime!
-  dup 0 do i notprime! 2 +loop
+  dup 4 > if
+    dup 4 do i notprime! 2 +loop
+  then
   begin
@@ Line 1,361: / Line 1,366: @@
     let mut sieve = vec![true; limit];
     if limit > 0 {
+        sieve[0] = false;
+    }
+    if limit > 1 {
         sieve[1] = false;
     }
-    for i in (0..limit).step_by(2) {
+    for i in (4..limit).step_by(2) {
         sieve[i] = false;
     }
@@ Line 1,385: / Line 1,393: @@
 fn strange_unique_prime_triplets(limit: usize, verbose: bool) {
-    let mut primes = Vec::new();
+    if limit < 6 {
-    if limit < 8 {
         return;
     }
+    let mut primes = Vec::new();
     let sieve = prime_sieve(limit * 3);
     for p in (3..limit).step_by(2) {
@@ Line 1,484: / Line 1,492: @@
     }
     var sieve = Array(repeating: true, count: limit)
-    sieve[1] = false
+    sieve[0] = false
-    for i in stride(from: 0, to: limit, by: 2) {
+    if limit > 1 {
-        sieve[i] = false
+        sieve[1] = false
+    }
+    if limit > 4 {
+        for i in stride(from: 4, to: limit, by: 2) {
+            sieve[i] = false
+        }
     }
     var p = 3
@@ Line 1,507: / Line 1,520: @@
 func strangeUniquePrimeTriplets(limit: Int, verbose: Bool) {
+    guard limit > 5 else {
+        return;
+    }
     let sieve = primeSieve(limit: 3 * limit)
     var primes: [Int] = []