Merge pull request #3 from jtr109/refine-3-sum

Refine 3 sum

Author: jtr109

.vscode/launch.json

@@ -1,67 +1,28 @@
 #![allow(dead_code)]
 
-use std::collections::HashMap;
-
 struct Solution {}
 
-struct Extractor {
-    nums: Vec<i32>,
-    nums_map: HashMap<i32, usize>,
-    sums_map: HashMap<Vec<i32>, ()>,
-}
-
-impl Extractor {
-    fn new(nums: &Vec<i32>) -> Self {
-        let mut sorted_nums = nums.clone();
-        sorted_nums.sort();
-        let mut nums_map = HashMap::new();
-        for &n in nums.iter() {
-            let count = nums_map.entry(n).or_insert(0);
-            *count += 1;
-        }
-        Extractor {
-            nums: sorted_nums,
-            nums_map,
-            sums_map: HashMap::new(),
-        }
-    }
-
-    fn get_expected(&self, n: &i32, m: &i32) -> Option<i32> {
-        let exp = 0 - n - m;
-        let count = self.nums_map.get(&exp).unwrap_or(&0);
-        if vec![*n, *m, exp].iter().filter(|&x| *x == exp).count() > *count {
-            return None;
-        }
-        Some(exp)
-    }
-
-    fn build_sums_map(&mut self) {
-        for (i, n) in self.nums.iter().enumerate() {
-            'second_loop: for m in self.nums[i + 1..].iter() {
-                if let Some(exp) = self.get_expected(n, m) {
-                    if exp < *m {
-                        // wrong sort
-                        break 'second_loop;
-                    } else {
-                        self.sums_map.insert(vec![*n, *m, exp], ());
+impl Solution {
+    pub fn three_sum(nums: Vec<i32>) -> Vec<Vec<i32>> {
+        let mut sorted = nums.clone();
+        sorted.sort();
+        let mut sums = vec![];
+        for i in 0..sorted.len() {
+            let mut j = i + 1;
+            let mut k = sorted.len() - 1;
+            while j < k {
+                let group = vec![sorted[i], sorted[j], sorted[k]];
+                match group.iter().sum::<i32>() {
+                    s if s < 0 => j += 1,
+                    s if s > 0 => k -= 1,
+                    _ => {
+                        sums.push(group);
+                        break;
                     }
-                } else {
-                    continue 'second_loop;
                 }
             }
         }
-    }
-
-    fn three_sum(&mut self) -> Vec<Vec<i32>> {
-        self.build_sums_map();
-        self.sums_map.keys().cloned().collect()
-    }
-}
-
-impl Solution {
-    pub fn three_sum(nums: Vec<i32>) -> Vec<Vec<i32>> {
-        let mut ext = Extractor::new(&nums);
-        ext.three_sum()
+        sums
     }
 }