Add submission for Day 1

day-1/.gitignore

@@ -0,0 +1,10 @@
+# Generated by Cargo
+# will have compiled files and executables
+/target/
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+Cargo.lock
+
+# These are backup files generated by rustfmt
+**/*.rs.bk

day-1/day_1.txt

@@ -0,0 +1,200 @@
+1833
+1949
+1745
+1863
+1422
+1980
+1695
+1233
+1407
+1971
+1486
+1922
+1802
+1689
+214
+1864
+1091
+1395
+1772
+1901
+1542
+1730
+1782
+1815
+1818
+1236
+1604
+1219
+1834
+1813
+1532
+1963
+2003
+1149
+1577
+1408
+1871
+1417
+1727
+1155
+1953
+1287
+1259
+1548
+1126
+1927
+1225
+1172
+11
+1301
+1869
+1808
+1238
+1989
+1027
+321
+1564
+636
+1847
+1877
+1716
+1275
+1738
+1054
+1966
+1019
+1256
+1940
+1821
+1914
+1556
+1389
+1020
+1293
+1935
+1804
+1945
+508
+1856
+1674
+1721
+1541
+1435
+1852
+1394
+2006
+1366
+1473
+1274
+623
+1701
+1842
+1954
+1999
+1195
+1246
+1967
+1153
+1851
+1294
+1152
+1812
+1732
+1030
+1956
+1132
+1948
+1865
+1835
+1231
+1975
+1759
+1843
+1379
+1657
+1267
+1062
+1850
+1817
+1543
+1805
+1252
+1974
+1161
+876
+1647
+1796
+1634
+1177
+1519
+1527
+1249
+1158
+2007
+1702
+1714
+1040
+1826
+1837
+1361
+1814
+1858
+1828
+1951
+1140
+1845
+1476
+1337
+1262
+1923
+1397
+1025
+1412
+1930
+1164
+1300
+1369
+1777
+1591
+1919
+1874
+1482
+2010
+1957
+1897
+1854
+1992
+1735
+1786
+1661
+1404
+1254
+1803
+1794
+1614
+1711
+1007
+1979
+1928
+1505
+2001
+1094
+2005
+1297
+1933
+1976
+1104
+1279
+1012
+1943
+1679
+1958
+1841
+1623
+1809
+1800
+919
+1620
+1936
+1209

day-1/src/main.rs

@@ -1,3 +1,57 @@
+use std::collections::HashSet;
+use std::fs::File;
+use std::io::prelude::*;
+use std::iter::FromIterator;
 fn main() {
-    println!("Hello, world!");
+    let mut file = File::open("day_1.txt").expect("Unable to open input file");
+    let mut contents = String::new();
+    file.read_to_string(&mut contents)
+        .expect("Unable to read file contents");
+    let expenses = contents
+        .lines()
+        .map(|line| line.parse::<i32>().expect("Unable to parse value to i32"))
+        .collect();
+    let expense = find_expenses(&expenses, 2020);
+    if let Some(val) = expense {
+        println!("{}", val);
+    } else {
+        println!("No 2 expenses found summing to 2020")
+    }
+
+    if let Some(val) = find_expenses_3(&expenses, 2020) {
+        println!("{}", val)
+    } else {
+        println!("No 3 expenses found summing to 2020")
+    }
+}
+
+fn find_expenses(expenses: &Vec<i32>, limit: i32) -> Option<i32> {
+    let mut part_exps: HashSet<i32> = HashSet::new();
+    let mut res: Option<i32> = None;
+    for expense in expenses {
+        let part_exp = limit - expense;
+        if part_exps.contains(&part_exp) {
+            res = Some(part_exp * expense);
+            break;
+        } else {
+            part_exps.insert(*expense);
+        }
+    }
+    res
+}
+
+fn find_expenses_3(expenses: &Vec<i32>, limit: i32) -> Option<i32> {
+    let expenses_set: HashSet<&i32> = HashSet::from_iter(expenses.iter());
+    let slash_expenses: Vec<i32> = expenses.iter().map(|exp| limit - exp).collect();
+    let mut res: Option<i32> = None;
+    for expense in expenses {
+        for slash_expense in &slash_expenses {
+            let diff = slash_expense - expense;
+            if expenses_set.contains(&diff) {
+                res = Some(diff * expense * (limit - slash_expense));
+                return res;
+            }
+        }
+    }
+    res
 }