complete 1644.rs 2887.rs 15552.rs 24767.rs 25710.rs 34031.rs

storage/zeta/rs/completed/1644.rs

@@ -0,0 +1,66 @@
+use std::io::stdin;
+
+fn get_primes_upto(n: u32) -> Vec<u32> {
+    let mut primes = vec![2];
+    for i in (3..=n).step_by(2) {
+        let mut flag = true;
+        for &p in primes.iter() {
+            if p > (i as f32).sqrt() as u32 {
+                break;
+            }
+            if i % p == 0 {
+                flag = false;
+                break;
+            }
+        }
+        if flag {
+            primes.push(i);
+        }
+    }
+
+    primes
+}
+
+fn get_ways_sum_primes(n: u32) -> usize {
+    let primes = get_primes_upto(n);
+
+    let cumulative_primes: Vec<u32> = std::iter::once(0)
+        .chain(primes.iter().scan(0, |acc, &p| {
+            *acc += p;
+            Some(*acc)
+        }))
+        .collect();
+
+    let mut lo: usize = 0;
+    let mut hi: usize = 1;
+
+    let mut ways: usize = 0;
+
+    let get_sum = |lo: usize, hi: usize| cumulative_primes[hi] - cumulative_primes[lo];
+
+    while lo <= hi && lo < cumulative_primes.len() && hi < cumulative_primes.len() {
+        let s = get_sum(lo, hi);
+        if n == s {
+            ways += 1;
+            lo += 1;
+        } else if n > s {
+            hi += 1;
+        } else {
+            lo += 1;
+        }
+    }
+
+    ways
+}
+
+fn main() {
+    let n = stdin()
+        .lines()
+        .next()
+        .unwrap()
+        .unwrap()
+        .parse::<u32>()
+        .unwrap();
+
+    println!("{}", get_ways_sum_primes(n));
+}