rust leetcode 204

rust-leetcode/README.md

@@ -81,4 +81,5 @@ Leetcode Rust 实现
 * [475 供暖器](src/leetcode_475.rs)
 * [605 种花问题](src/leetcode_605.rs)
 * [面试题10- I 斐波那契数列](src/interview_10_01.rs)
-* [633 平方数之和](src/leetcode_633.rs)
\ No newline at end of file
+* [633 平方数之和](src/leetcode_633.rs)
+* [204 计数质数](src/leetcode_204.rs)
\ No newline at end of file

rust-leetcode/src/leetcode_204.rs

+use std::collections::HashSet;
+
+use crate::pre_structs::Solution;
+
+///204. 计数质数
+impl Solution {
+    //772MS,2.1MB
+    pub fn count_primes(n: i32) -> i32 {
+        fn is_primes(num: i32) -> bool {
+            let mut cnt = 0;
+            if num < 2 {
+                return false;
+            }
+            if num == 2 {
+                return true;
+            }
+            for i in 2..=f32::sqrt(num as f32) as i32 {
+                if num % i == 0 {
+                    return false;
+                }
+            }
+            true
+        }
+        let mut cnt = 0;
+        for i in 0..n {
+            if is_primes(i) {
+                cnt += 1;
+            }
+        }
+        cnt
+    }
+
+    //排除法 埃拉托色尼筛选法
+    //12MS,3.4MB
+    pub fn count_primes2(n: i32) -> i32 {
+        if n < 2 {
+            return 0;
+        }
+        let mut bit_set = vec![true; n as usize];
+        let mut i = 2;
+        while i * i < n {
+            if bit_set[i as usize] {
+                let mut j = i * i;
+                while j < n {
+                    bit_set[j as usize] = false;
+                    j += i;
+                }
+            }
+            i += 1;
+        }
+        let cnt = bit_set
+            .iter()
+            .enumerate()
+            .filter(|(i, &x)| i >= &2 && i < &(n as usize) && x == true)
+            .count();
+        cnt as i32
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::pre_structs::Solution;
+
+    #[test]
+    fn count_primes() {
+        let ret = Solution::count_primes(10);
+        let ret2 = Solution::count_primes2(10);
+        assert!(ret == ret2);
+    }
+}

rust-leetcode/src/main.rs

@@ -41,6 +41,7 @@ pub mod leetcode_14;
 pub mod leetcode_1403;
 pub mod leetcode_1413;
 pub mod leetcode_20;
+pub mod leetcode_204;
 pub mod leetcode_292;
 pub mod leetcode_35;
 pub mod leetcode_38;