Finish assignments for course 2

src/main.rs

@@ -83,6 +83,11 @@ fn c2a4() {
     println!("c2a4={:?}", r);
 }
 
+#[allow(dead_code)]
+fn c3a1() {
+	println!("continue here");
+}
+
 fn main() {
     // c1a2();
     // c1a3();
@@ -90,5 +95,6 @@ fn main() {
     // c2a1();
     // c2a2();
     // c2a3();
-    c2a4();
+    // c2a4();
+    c3a1();
 }

src/two_sum.rs

@@ -1,13 +1,32 @@
+use std::collections::HashSet;
+use std::iter::FromIterator;
 
-fn two_sum(t: i64, xs_vec: &Vec<i64>) {
-
+fn two_sum(t: i64, xs: &Vec<i64>, ys: &HashSet<i64>) -> bool {
+	for &x in xs {
+		let y = t - x;
+		if x != y && ys.contains(&y) {
+			return true;
+		}
+	}
+	false
 }
 
 pub fn find_two_sums(xs: Vec<i64>) -> usize {
 
+	let mut xs_min: Vec<i64> = xs.to_vec();
+	xs_min.retain(|&i| i < 0);
 
+	let mut xs_max: Vec<i64> = xs.to_vec();
+	xs_max.retain(|&i| i >= 0);
+	let xs_max_set: HashSet<i64> = HashSet::from_iter(xs_max);
 
-	0
+	let mut r: usize = 0;
+	for t in -10000..10001 {
+		if two_sum(t, &xs_min, &xs_max_set) {
+			r += 1
+		}
+	}
+	r
 }