Solved day1

input/day1.txt

@@ -0,0 +1,200 @@
+1254
+1313
+1456
+1782
+1742
+1391
+1273
+1286
+1373
+1891
+1188
+1994
+1887
+1816
+1984
+961
+1428
+1105
+1123
+1699
+1154
+1953
+1977
+1450
+1696
+1068
+1241
+1926
+1228
+1591
+1789
+1966
+1508
+1193
+1190
+1654
+444
+1282
+1169
+1165
+1778
+1669
+1570
+1671
+1845
+1208
+1728
+1798
+847
+1300
+1817
+1200
+1297
+1658
+1296
+1571
+1991
+1305
+1314
+1903
+1472
+1359
+1506
+1999
+1877
+1168
+1137
+1288
+1083
+1656
+413
+1430
+1408
+1397
+1846
+1218
+684
+1234
+2007
+900
+1604
+1460
+1848
+1693
+1324
+1401
+1968
+1918
+1975
+1665
+1413
+1874
+1852
+1521
+1753
+1229
+1940
+1650
+1976
+1235
+1130
+1927
+1365
+1908
+1441
+1302
+1986
+1449
+1692
+1944
+1277
+1312
+1826
+1231
+1289
+1814
+1170
+1606
+1608
+1773
+1883
+1936
+1626
+1497
+1860
+1673
+1295
+2005
+1481
+1995
+1734
+1646
+1557
+1298
+1174
+1894
+1309
+1240
+1982
+1414
+1799
+1620
+1863
+1220
+1642
+508
+1146
+1187
+1253
+1284
+1952
+1527
+1610
+1333
+1221
+1362
+1457
+1721
+1493
+1330
+156
+1647
+1841
+1724
+2000
+1398
+1745
+1985
+1269
+1722
+2001
+1923
+1395
+1094
+1140
+1958
+1239
+1336
+1588
+1338
+1750
+1757
+1444
+1822
+1335
+1941
+1865
+1767
+1881
+1499
+1157
+1990
+1210
+1779
+1201
+1784
+1961
+1476
+1861
+1468

input/day1_example.txt

@@ -0,0 +1,6 @@
+1721
+979
+366
+299
+675
+1456

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
+
+}