add "product of array except self" in rust

product_of_array_except_self/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "product_of_array_except_self"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

product_of_array_except_self/src/main.rs

@@ -0,0 +1,57 @@
+struct Solution;
+
+enum Zeros {
+    None,
+    One(usize),
+    Many,
+}
+
+impl Solution {
+    pub fn product_except_self(nums: Vec<i32>) -> Vec<i32> {
+        let mut out = vec![0i32; nums.len()];
+        let nums = nums.as_slice();
+        let zeros = count_zeros(nums);
+
+        match zeros {
+            Zeros::None => {
+                let prod: i32 = nums.iter().product();
+                for (i, x) in nums.iter().enumerate() {
+                    out[i] = prod / x;
+                }
+            }
+            Zeros::One(z) => {
+                let left = if z == 0 {
+                    1
+                } else {
+                    nums[0..z].iter().product()
+                };
+                let right = if z == nums.len() - 1 {
+                    1
+                } else {
+                    nums[(z + 1)..].iter().product()
+                };
+                out[z] = left * right;
+            }
+            _ => {}
+        }
+        out
+    }
+}
+
+fn count_zeros(nums: &[i32]) -> Zeros {
+    let mut zeros = std::collections::HashSet::new();
+    for (i, n) in nums.iter().enumerate() {
+        if *n == 0i32 {
+            zeros.insert(i);
+        }
+    }
+    match zeros.len() {
+        0 => Zeros::None,
+        1 => Zeros::One(*zeros.iter().next().unwrap()),
+        _ => Zeros::Many,
+    }
+}
+
+fn main() {
+    println!("Hello, world!");
+}