Added day 1 pt 2

inputs/day1.sample.txt

@@ -0,0 +1,11 @@
+199
+200
+208
+210
+200
+207
+240
+269
+260
+263
+

src/main.rs

@@ -1,3 +1,6 @@
+#![feature(test)]
+extern crate test;
+
 const INPUT: &'static str = include_str!("../inputs/day1.txt");
 
 fn depths() -> Vec<u64> {
@@ -8,15 +11,39 @@ fn depths() -> Vec<u64> {
         .collect()
 }
 
-fn main() {
-    let days = depths();
+fn solution(depths: &[u64]) -> i32 {
     let mut count = 0;
 
-    for set in days.windows(2) {
-        if set[1] > set[0] {
+    // For a window size of 3, We can consider a window size of 4
+    // A + B + C && B + C + D
+    // Since B, C are shared between the two consecutive sets,
+    // We only need to compare A and D
+    for set in depths.windows(4) {
+        if set[0] < set[3] {
             count += 1;
         }
     }
 
+    count
+}
+
+fn main() {
+    let depths = &depths();
+    let count = solution(depths);
     println!("increased {} times", count);
 }
+
+#[bench]
+fn solution_bench(b: &mut test::Bencher) {
+    let depths = depths();
+
+    b.iter(|| {
+        let v = solution(&depths);
+        test::black_box(v);
+    })
+}
+
+#[test]
+fn solution_test() {
+    assert_eq!(solution(&depths()), 1429);
+}