-
Notifications
You must be signed in to change notification settings - Fork 0
/
day09.go
81 lines (72 loc) · 1.68 KB
/
day09.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package day09 solves AoC 2020 day 9.
package day09
import (
"github.com/fis/aoc/glue"
)
func init() {
glue.RegisterSolver(2020, 9, glue.IntSolver(solve))
}
func solve(data []int) ([]string, error) {
invalid := validate(data, 25)
min, max := findSum(data, invalid)
return glue.Ints(invalid, min+max), nil
}
func validate(data []int, win int) int {
sums := make(map[int]int)
for i, x := range data[:win-1] {
for _, y := range data[i+1 : win] {
sums[x+y] = sums[x+y] + 1
}
}
for i := win; i < len(data); i++ {
n := data[i]
if sums[n] == 0 {
return n
}
o := data[i-win]
for _, x := range data[i-win+1 : i] {
sums[o+x] = sums[o+x] - 1
sums[n+x] = sums[n+x] + 1
}
}
return -1
}
func findSum(data []int, key int) (min, max int) {
l, r, sum := 0, 0, data[0]
for {
if sum < key {
r++
sum += data[r]
} else if sum > key {
sum -= data[l]
l++
} else {
return minMax(data[l : r+1])
}
}
}
func minMax(data []int) (min, max int) {
min, max = data[0], data[0]
for _, n := range data[1:] {
if n < min {
min = n
}
if n > max {
max = n
}
}
return min, max
}