main.go

package main

import "fmt"

var expenseReport = []int{
	1975,
	1600,
	113,
	1773,
	1782,
	1680,
	1386,
	1682,
	1991,
	1640,
	1760,
	1236,
	1159,
	1259,
	1279,
	1739,
	1826,
	1888,
	1072,
	416,
	1632,
	1656,
	1273,
	1631,
	1079,
	1807,
	1292,
	1128,
	1841,
	1915,
	1619,
	1230,
	1950,
	1627,
	1966,
	774,
	1425,
	1983,
	1616,
	1633,
	1559,
	1925,
	960,
	1407,
	1708,
	1211,
	1666,
	1910,
	1960,
	1125,
	1242,
	1884,
	1829,
	1881,
	1585,
	1731,
	1753,
	1784,
	1095,
	1267,
	1756,
	1226,
	1107,
	1664,
	1710,
	2000,
	1181,
	1997,
	1607,
	1889,
	1613,
	1859,
	1479,
	1763,
	1692,
	1967,
	522,
	1719,
	1816,
	1714,
	1331,
	1976,
	1160,
	1899,
	1906,
	1783,
	1061,
	2006,
	1993,
	1717,
	2009,
	1563,
	1733,
	1866,
	1651,
	1437,
	1517,
	1113,
	1743,
	1240,
	1629,
	1868,
	1912,
	1296,
	1873,
	1673,
	1996,
	1814,
	1215,
	1927,
	1956,
	1970,
	1887,
	1702,
	1495,
	1754,
	1621,
	1055,
	1538,
	1693,
	1840,
	1685,
	1752,
	1933,
	1727,
	1648,
	1792,
	1734,
	1305,
	1446,
	1764,
	1890,
	1904,
	1560,
	1698,
	1645,
	1214,
	1516,
	1064,
	1729,
	1835,
	1642,
	1932,
	1683,
	962,
	1081,
	1943,
	1502,
	1622,
	196,
	1972,
	1916,
	1850,
	1205,
	1971,
	1937,
	1575,
	1401,
	1351,
	2005,
	1917,
	1670,
	1388,
	1051,
	1941,
	1751,
	1169,
	510,
	217,
	1948,
	1120,
	1635,
	1636,
	1511,
	1691,
	1589,
	1410,
	1902,
	1572,
	1871,
	1423,
	1114,
	1806,
	1282,
	1193,
	1974,
	388,
	1398,
	1992,
	1263,
	1786,
	1723,
	1206,
	1363,
	1177,
	1646,
	1231,
	1140,
	1088,
	1322,
}

func main() {
	fmt.Printf("first solution: %d\n", first())
	fmt.Printf("second solution: %d\n", second())
}

func first() int {
	for _, exp1 := range expenseReport {
		for _, exp2 := range expenseReport {
			if exp1 == exp2 {
				continue
			}

			if exp1+exp2 == 2020 {
				return exp1 * exp2
			}
		}
	}

	return 0
}

func second() int {
	for _, exp1 := range expenseReport {
		for _, exp2 := range expenseReport {
			if exp1 == exp2 {
				continue
			}

			for _, exp3 := range expenseReport {
				if exp1 == exp3 || exp2 == exp3 {
					continue
				}

				if exp1+exp2+exp3 == 2020 {
					return exp1 * exp2 * exp3
				}
			}
		}
	}

	return 0
}