Solved day1

src/day1.rs

@@ -0,0 +1,90 @@
+
+use super::util;
+
+pub fn solve() {
+    let lines = util::read_file("input/day1.txt");
+    let mut nums: Vec<u32> = lines.iter().map(|s|s.parse::<u32>().unwrap()).collect();
+    nums.sort();
+
+    let part1 = find_pairs_summing_to(&nums, 2020);
+    println!("Day 1 Part 1: {}", part1.0 * part1.1);
+
+    let part2 = find_triplet_summing_to(&nums, 2020);
+    println!("Day 1 Part 2: {}", part2.0 * part2.1 * part2.2);
+}
+
+fn find_pairs_summing_to(nums: &Vec<u32>, target: u32) -> (u32, u32)  {
+
+    let mut i:usize = 0;
+    let mut j:usize = nums.len() - 1;
+
+    loop {
+        if j < i {
+            panic!("Couldn't find match");
+        }
+        let sum = nums[i] + nums[j];
+        if sum < target {
+            i += 1;
+        } else if sum > target {
+            j -= 1;
+        } else {
+            return (nums[i], nums[j]);
+        }
+    }
+}
+
+fn find_triplet_summing_to(nums: &Vec<u32>, target: u32) -> (u32, u32, u32){
+
+
+
+    for i in 0..nums.len() {
+        for j in (0..nums.len()).rev() {
+
+            if j <= i {
+                break;
+            }
+
+            let n1 = nums[i];
+            let n2 = nums[j];
+            if target < n1 + n2 {
+                continue;
+            }
+            let n3_target = target - n1 - n2;
+            let res = nums.binary_search(&n3_target);
+            if res.is_ok() && res.unwrap() > i && res.unwrap() < j {
+                return (n1, n2, n3_target);
+            }
+        }
+    }
+    panic!("Couldn't find match!");
+
+    //
+    // let mut i:usize = 0;
+    // let mut j:usize = nums.len() - 1;
+    // loop {
+    //     if j < i {
+    //
+    //         // Reset with i one higher:
+    //         i += 1;
+    //         j = nums.len() - 1;
+    //     }
+    //
+    //     let n1 = nums[i];
+    //     let n2 = nums[j];
+    //     let sum = n1 + n2;
+    //     if sum + n1 > target {
+    //         j -= 1;
+    //     } else {
+    //         // See if we can find a third number between i and j that makes the sum equal to the target
+    //         let n3_target = target - sum;
+    //         let res = nums.binary_search(&n3_target);
+    //         if res.is_ok() {
+    //             // Found it!
+    //             return (n1, n2, n3_target)
+    //         } else {
+    //             j -= 1;
+    //         }
+    //     }
+    // }
+
+}

src/util.rs

@@ -0,0 +1,13 @@
+use std::fs;
+
+pub fn read_file(filename: &str) -> Vec<String> {
+
+    let contents = fs::read_to_string(filename)
+        .expect("Couldn't read file!");
+
+    let mut res: Vec<String> = Vec::new();
+    contents.lines().for_each(|l| res.push(String::from(l)));
+
+    res
+
+}