reuse array for product

product_of_array_except_self/src/main.rs

@@ -8,29 +8,29 @@ enum Zeros {
 
 impl Solution {
     pub fn product_except_self(nums: Vec<i32>) -> Vec<i32> {
-        let mut out = vec![0i32; nums.len()];
+        let mut out = nums;
-        let nums = nums.as_slice();
+        let nums = &mut out;
         let zeros = count_zeros(nums);
 
         match zeros {
             Zeros::None => {
                 let prod: i32 = nums.iter().product();
-                for (i, x) in nums.iter().enumerate() {
+                for x in nums.iter_mut() {
-                    out[i] = prod / x;
+                    *x = prod / *x;
                 }
             }
             Zeros::One(z) => {
-                let left = if z == 0 {
+                let (left, right) = nums.split_at(z);
-                    1
+                let left = if z == 0 { 1 } else { left.iter().product() };
-                } else {
-                    nums[0..z].iter().product()
-                };
                 let right = if z == nums.len() - 1 {
                     1
                 } else {
-                    nums[(z + 1)..].iter().product()
+                    right[1..].iter().product()
                 };
-                out[z] = left * right;
+                for x in nums.iter_mut() {
+                    *x = 0;
+                }
+                nums[z] = left * right;
             }
             _ => {}
         }
@@ -39,19 +39,22 @@ impl Solution {
 }
 
 fn count_zeros(nums: &[i32]) -> Zeros {
-    let mut zeros = std::collections::HashSet::new();
+    let mut out = Zeros::None;
+    let zs = 0;
     for (i, n) in nums.iter().enumerate() {
         if *n == 0i32 {
-            zeros.insert(i);
+            if zs == 0 {
+                out = Zeros::One(i);
+            } else {
+                out = Zeros::Many;
+                break;
+            }
         }
     }
-    match zeros.len() {
+    out
-        0 => Zeros::None,
-        1 => Zeros::One(*zeros.iter().next().unwrap()),
-        _ => Zeros::Many,
-    }
 }
 
 fn main() {
-    println!("Hello, world!");
+    let p = Solution::product_except_self(vec![-1, 1, 0, -3, 3]);
+    dbg!(p);
 }