-
Notifications
You must be signed in to change notification settings - Fork 1
/
candy.go
100 lines (95 loc) · 2.13 KB
/
candy.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
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
package candy
import (
"github.com/catorpilor/leetcode/utils"
)
func numOfCandies(ratings []int) int {
// return useBruteForce(ratings)
// return useTwoArray(ratings)
return useOneArray(ratings)
}
// useBruteForce time complexity O(N^2), space complexity O(N)
func useBruteForce(ratings []int) int {
n := len(ratings)
if n <= 1 {
return n
}
flag := true
store := make([]int, n)
for i := range store {
store[i] = 1
}
for flag {
flag = false
for i := 0; i < n; i++ {
if i > 0 && ratings[i] > ratings[i-1] && store[i] <= store[i-1] {
store[i] = store[i-1] + 1 // update need to validate
flag = true
}
if i < n-1 && ratings[i] > ratings[i+1] && store[i] <= store[i+1] {
store[i] = store[i+1] + 1 // update need to validate
flag = true
}
}
}
var ans int
for i := range store {
ans += store[i]
}
return ans
}
// useTwoArray time complexity O(N), space complexity O(N)
func useTwoArray(ratings []int) int {
n := len(ratings)
if n <= 1 {
return n
}
// leftTurn just to satisfy the left side rule.
// rightTurn just to satisfy the right side rule.
leftTurn, rightTurn := make([]int, n), make([]int, n)
leftTurn[0], rightTurn[n-1] = 1, 1
for i := 1; i < n; i++ {
if ratings[i] <= ratings[i-1] {
leftTurn[i] = 1
} else {
leftTurn[i] = leftTurn[i-1] + 1
}
}
for i := n - 2; i >= 0; i-- {
if ratings[i] <= ratings[i+1] {
rightTurn[i] = 1
} else {
rightTurn[i] = rightTurn[i+1] + 1
}
}
var ans int
for i := 0; i < n; i++ {
ans += utils.Max(leftTurn[i], rightTurn[i])
}
return ans
}
// useOneArray time complexity O(N), space compleixyt O(N)
func useOneArray(ratings []int) int {
n := len(ratings)
if n <= 1 {
return n
}
candies := make([]int, n)
for i := range candies {
candies[i] = 1
}
// left turn only to satisfy the left side rule.
for i := 1; i < n; i++ {
if ratings[i] > ratings[i-1] {
candies[i] = candies[i-1] + 1
}
}
var ans int
ans += candies[n-1] // the right most one only satisfy the left rule.
for i := n - 2; i >= 0; i-- {
if ratings[i] > ratings[i+1] {
candies[i] = utils.Max(candies[i], candies[i+1]+1)
}
ans += candies[i]
}
return ans
}