From 77828d0eb94b3bcb71b0a42478400fc08ed40523 Mon Sep 17 00:00:00 2001
From: Felix Martin <mail@felixm.de>
Date: Sat, 12 Dec 2020 10:53:27 -0500
Subject: [PATCH] Finish assignments for course 2

---
 misc/two_sums.py | 25 +++++++++++++++++++++++++
 src/main.rs      |  8 +++++++-
 src/two_sum.rs   | 25 ++++++++++++++++++++++---
 3 files changed, 54 insertions(+), 4 deletions(-)
 create mode 100644 misc/two_sums.py

diff --git a/misc/two_sums.py b/misc/two_sums.py
new file mode 100644
index 0000000..c71f212
--- /dev/null
+++ b/misc/two_sums.py
@@ -0,0 +1,25 @@
+
+def two_sum(t, xs_list, xs_set):
+    for x in xs:
+        y = t - x
+        if x != y and y in xs_set:
+            return True
+    return False
+
+
+if __name__ == "__main__":
+    with open("../data/c2a4.txt") as f:
+        xs = list(map(int, f.readlines()))
+
+    xs_min = [x for x in xs if x < 0]
+    xs_max_set = set([x for x in xs if x > 0])
+
+    limit = 10000
+    two_sums = 0
+    for t in range(-limit, limit + 1):
+        if t % 10 == 0:
+            print(t)
+        if two_sum(t, xs_min, xs_max_set):
+            two_sums += 1
+
+    print(two_sums)
diff --git a/src/main.rs b/src/main.rs
index a04d0d1..37b17fa 100644
--- a/src/main.rs
+++ b/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();
 }
diff --git a/src/two_sum.rs b/src/two_sum.rs
index cd38aa0..495d3a4 100644
--- a/src/two_sum.rs
+++ b/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
 }