From c0325eedf56ef3176d86cdac796b3d5f548963eb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=A2=A6=E5=A2=83=E8=BF=B7=E7=A6=BB?=
 <dreamylost@outlook.com>
Date: Fri, 22 May 2020 17:54:59 +0800
Subject: [PATCH] rust leetcode 204

---
 rust-leetcode/README.md           |  3 +-
 rust-leetcode/src/leetcode_204.rs | 70 +++++++++++++++++++++++++++++++
 rust-leetcode/src/main.rs         |  1 +
 3 files changed, 73 insertions(+), 1 deletion(-)
 create mode 100644 rust-leetcode/src/leetcode_204.rs

diff --git a/rust-leetcode/README.md b/rust-leetcode/README.md
index 564089f9..85672f39 100644
--- a/rust-leetcode/README.md
+++ b/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
diff --git a/rust-leetcode/src/leetcode_204.rs b/rust-leetcode/src/leetcode_204.rs
new file mode 100644
index 00000000..0506d820
--- /dev/null
+++ b/rust-leetcode/src/leetcode_204.rs
@@ -0,0 +1,70 @@
+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);
+    }
+}
diff --git a/rust-leetcode/src/main.rs b/rust-leetcode/src/main.rs
index ea1f2388..b9982cbe 100644
--- a/rust-leetcode/src/main.rs
+++ b/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;
-- 
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