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Commit 85beeb5

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feat: add solutions to lc problem: No.0381. Insert Delete Get Random O(1) - Duplicates allowed
1 parent bf65776 commit 85beeb5

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-65
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5 files changed

+333
-65
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‎solution/0300-0399/0380.Insert Delete GetRandom O(1)/README.md‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -50,7 +50,7 @@ randomSet.getRandom();
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哈希表存放每个元素的值和对应的下标,而动态列表在每个下标位置存放每个元素。由动态列表实现元素的随机返回。
5252

53-
注意,在 `remove()` 的时候,先将列表的最后一个元素设置到待删元素的位置上,然后删除最后一个元素,这样在删除元素的时候,不需要挪动一大批元素,从而实现 `O(1)` 时间内操作。
53+
注意,在 `remove()` 实现上,将列表的最后一个元素设置到待删元素的位置上,然后删除最后一个元素,这样在删除元素的时候,不需要挪动一大批元素,从而实现 `O(1)` 时间内操作。
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<!-- tabs:start -->
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‎solution/0300-0399/0381.Insert Delete GetRandom O(1) - Duplicates allowed/README.md‎

Lines changed: 118 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -40,27 +40,142 @@ collection.remove(1);
4040
collection.getRandom();
4141
</pre>
4242

43-
4443
## 解法
4544

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<!-- 这里可写通用的实现逻辑 -->
4746

47+
"哈希表 + 动态列表"实现。
48+
49+
哈希表存放每个元素的值和对应的下标集合,而动态列表在每个下标位置存放每个元素。由动态列表实现元素的随机返回。
50+
51+
注意,在 `remove()` 实现上,将列表的最后一个元素设置到待删元素的位置上,然后删除最后一个元素,这样在删除元素的时候,不需要挪动一大批元素,从而实现 `O(1)` 时间内操作。
52+
4853
<!-- tabs:start -->
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5055
### **Python3**
5156

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<!-- 这里可写当前语言的特殊实现逻辑 -->
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5459
```python
55-
60+
class RandomizedCollection:
61+
62+
def __init__(self):
63+
"""
64+
Initialize your data structure here.
65+
"""
66+
self.m = {}
67+
self.l = []
68+
69+
def insert(self, val: int) -> bool:
70+
"""
71+
Inserts a value to the collection. Returns true if the collection did not already contain the specified element.
72+
"""
73+
idx_set = self.m.get(val, set())
74+
idx_set.add(len(self.l))
75+
self.m[val] = idx_set
76+
self.l.append(val)
77+
return len(idx_set) == 1
78+
79+
def remove(self, val: int) -> bool:
80+
"""
81+
Removes a value from the collection. Returns true if the collection contained the specified element.
82+
"""
83+
if val not in self.m:
84+
return False
85+
idx_set = self.m[val]
86+
idx = list(idx_set)[0]
87+
last_idx = len(self.l) - 1
88+
self.l[idx] = self.l[last_idx]
89+
idx_set.remove(idx)
90+
91+
last_idx_set = self.m[self.l[last_idx]]
92+
if last_idx in last_idx_set:
93+
last_idx_set.remove(last_idx)
94+
if idx < last_idx:
95+
last_idx_set.add(idx)
96+
if not idx_set:
97+
self.m.pop(val)
98+
self.l.pop()
99+
return True
100+
101+
def getRandom(self) -> int:
102+
"""
103+
Get a random element from the collection.
104+
"""
105+
return -1 if len(self.l) == 0 else random.choice(self.l)
106+
107+
108+
109+
# Your RandomizedCollection object will be instantiated and called as such:
110+
# obj = RandomizedCollection()
111+
# param_1 = obj.insert(val)
112+
# param_2 = obj.remove(val)
113+
# param_3 = obj.getRandom()
56114
```
57115

58116
### **Java**
59117

60118
<!-- 这里可写当前语言的特殊实现逻辑 -->
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62120
```java
63-
121+
class RandomizedCollection {
122+
private Map<Integer, Set<Integer>> m;
123+
private List<Integer> l;
124+
private Random rnd;
125+
126+
/** Initialize your data structure here. */
127+
public RandomizedCollection() {
128+
m = new HashMap<>();
129+
l = new ArrayList<>();
130+
rnd = new Random();
131+
}
132+
133+
/** Inserts a value to the collection. Returns true if the collection did not already contain the specified element. */
134+
public boolean insert(int val) {
135+
Set<Integer> idxSet = m.getOrDefault(val, new HashSet<>());
136+
idxSet.add(l.size());
137+
m.put(val, idxSet);
138+
l.add(val);
139+
return idxSet.size() == 1;
140+
}
141+
142+
/** Removes a value from the collection. Returns true if the collection contained the specified element. */
143+
public boolean remove(int val) {
144+
if (!m.containsKey(val)) {
145+
return false;
146+
}
147+
Set<Integer> idxSet = m.get(val);
148+
int idx = idxSet.iterator().next();
149+
int lastIdx = l.size() - 1;
150+
l.set(idx, l.get(lastIdx));
151+
idxSet.remove(idx);
152+
153+
Set<Integer> lastIdxSet = m.get(l.get(lastIdx));
154+
lastIdxSet.remove(lastIdx);
155+
if (idx < lastIdx) {
156+
lastIdxSet.add(idx);
157+
}
158+
if (idxSet.isEmpty()) {
159+
m.remove(val);
160+
}
161+
l.remove(lastIdx);
162+
return true;
163+
}
164+
165+
/** Get a random element from the collection. */
166+
public int getRandom() {
167+
int size = l.size();
168+
return size == 0 ? -1 : l.get(rnd.nextInt(size));
169+
}
170+
}
171+
172+
/**
173+
* Your RandomizedCollection object will be instantiated and called as such:
174+
* RandomizedCollection obj = new RandomizedCollection();
175+
* boolean param_1 = obj.insert(val);
176+
* boolean param_2 = obj.remove(val);
177+
* int param_3 = obj.getRandom();
178+
*/
64179
```
65180

66181
### **...**

‎solution/0300-0399/0381.Insert Delete GetRandom O(1) - Duplicates allowed/README_EN.md‎

Lines changed: 112 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -52,13 +52,123 @@ randomizedCollection.getRandom(); // getRandom should return 1 and 2 both equall
5252
### **Python3**
5353

5454
```python
55-
55+
class RandomizedCollection:
56+
57+
def __init__(self):
58+
"""
59+
Initialize your data structure here.
60+
"""
61+
self.m = {}
62+
self.l = []
63+
64+
def insert(self, val: int) -> bool:
65+
"""
66+
Inserts a value to the collection. Returns true if the collection did not already contain the specified element.
67+
"""
68+
idx_set = self.m.get(val, set())
69+
idx_set.add(len(self.l))
70+
self.m[val] = idx_set
71+
self.l.append(val)
72+
return len(idx_set) == 1
73+
74+
def remove(self, val: int) -> bool:
75+
"""
76+
Removes a value from the collection. Returns true if the collection contained the specified element.
77+
"""
78+
if val not in self.m:
79+
return False
80+
idx_set = self.m[val]
81+
idx = list(idx_set)[0]
82+
last_idx = len(self.l) - 1
83+
self.l[idx] = self.l[last_idx]
84+
idx_set.remove(idx)
85+
86+
last_idx_set = self.m[self.l[last_idx]]
87+
if last_idx in last_idx_set:
88+
last_idx_set.remove(last_idx)
89+
if idx < last_idx:
90+
last_idx_set.add(idx)
91+
if not idx_set:
92+
self.m.pop(val)
93+
self.l.pop()
94+
return True
95+
96+
def getRandom(self) -> int:
97+
"""
98+
Get a random element from the collection.
99+
"""
100+
return -1 if len(self.l) == 0 else random.choice(self.l)
101+
102+
103+
104+
# Your RandomizedCollection object will be instantiated and called as such:
105+
# obj = RandomizedCollection()
106+
# param_1 = obj.insert(val)
107+
# param_2 = obj.remove(val)
108+
# param_3 = obj.getRandom()
56109
```
57110

58111
### **Java**
59112

60113
```java
61-
114+
class RandomizedCollection {
115+
private Map<Integer, Set<Integer>> m;
116+
private List<Integer> l;
117+
private Random rnd;
118+
119+
/** Initialize your data structure here. */
120+
public RandomizedCollection() {
121+
m = new HashMap<>();
122+
l = new ArrayList<>();
123+
rnd = new Random();
124+
}
125+
126+
/** Inserts a value to the collection. Returns true if the collection did not already contain the specified element. */
127+
public boolean insert(int val) {
128+
Set<Integer> idxSet = m.getOrDefault(val, new HashSet<>());
129+
idxSet.add(l.size());
130+
m.put(val, idxSet);
131+
l.add(val);
132+
return idxSet.size() == 1;
133+
}
134+
135+
/** Removes a value from the collection. Returns true if the collection contained the specified element. */
136+
public boolean remove(int val) {
137+
if (!m.containsKey(val)) {
138+
return false;
139+
}
140+
Set<Integer> idxSet = m.get(val);
141+
int idx = idxSet.iterator().next();
142+
int lastIdx = l.size() - 1;
143+
l.set(idx, l.get(lastIdx));
144+
idxSet.remove(idx);
145+
146+
Set<Integer> lastIdxSet = m.get(l.get(lastIdx));
147+
lastIdxSet.remove(lastIdx);
148+
if (idx < lastIdx) {
149+
lastIdxSet.add(idx);
150+
}
151+
if (idxSet.isEmpty()) {
152+
m.remove(val);
153+
}
154+
l.remove(lastIdx);
155+
return true;
156+
}
157+
158+
/** Get a random element from the collection. */
159+
public int getRandom() {
160+
int size = l.size();
161+
return size == 0 ? -1 : l.get(rnd.nextInt(size));
162+
}
163+
}
164+
165+
/**
166+
* Your RandomizedCollection object will be instantiated and called as such:
167+
* RandomizedCollection obj = new RandomizedCollection();
168+
* boolean param_1 = obj.insert(val);
169+
* boolean param_2 = obj.remove(val);
170+
* int param_3 = obj.getRandom();
171+
*/
62172
```
63173

64174
### **...**

‎solution/0300-0399/0381.Insert Delete GetRandom O(1) - Duplicates allowed/Solution.java‎

Lines changed: 48 additions & 59 deletions
Original file line numberDiff line numberDiff line change
@@ -1,63 +1,52 @@
11
class RandomizedCollection {
2-
3-
private List<Integer> list;
4-
private Map<Integer, Set<Integer>> map;
5-
private Random random;
6-
7-
/** Initialize your data structure here. */
8-
public RandomizedCollection() {
9-
list = new ArrayList<>();
10-
map = new HashMap<>();
11-
random = new Random();
12-
}
13-
14-
/**
15-
* Inserts a value to the set. Returns true if the set did not already contain
16-
* the specified element.
17-
*/
18-
public boolean insert(int val) {
19-
boolean flag = false;
20-
if (!map.containsKey(val)) {
21-
flag = true;
22-
map.put(val, new HashSet<Integer>());
23-
}
24-
map.get(val).add(list.size());
25-
list.add(val);
26-
return flag;
27-
}
28-
29-
/**
30-
* Removes a value from the set. Returns true if the set contained the specified
31-
* element.
32-
*/
33-
public boolean remove(int val) {
34-
if (!map.containsKey(val)) {
35-
return false;
36-
}
37-
int removed = map.get(val).iterator().next();
38-
map.get(val).remove(removed);
39-
if (removed < list.size() - 1) {
40-
Integer tail = list.get(list.size() - 1);
41-
list.set(removed, tail);
42-
map.get(tail).remove(list.size() - 1);
43-
map.get(tail).add(removed);
44-
}
45-
list.remove(list.size() - 1);
46-
if (map.get(val).size() == 0) {
47-
map.remove(val);
48-
}
49-
return true;
50-
}
51-
52-
/** Get a random element from the set. */
53-
public int getRandom() {
54-
if (list.size() == 0) {
55-
return 0;
56-
}
57-
58-
return list.get(random.nextInt(list.size()));
59-
}
60-
2+
private Map<Integer, Set<Integer>> m;
3+
private List<Integer> l;
4+
private Random rnd;
5+
6+
/** Initialize your data structure here. */
7+
public RandomizedCollection() {
8+
m = new HashMap<>();
9+
l = new ArrayList<>();
10+
rnd = new Random();
11+
}
12+
13+
/** Inserts a value to the collection. Returns true if the collection did not already contain the specified element. */
14+
public boolean insert(int val) {
15+
Set<Integer> idxSet = m.getOrDefault(val, new HashSet<>());
16+
idxSet.add(l.size());
17+
m.put(val, idxSet);
18+
l.add(val);
19+
return idxSet.size() == 1;
20+
}
21+
22+
/** Removes a value from the collection. Returns true if the collection contained the specified element. */
23+
public boolean remove(int val) {
24+
if (!m.containsKey(val)) {
25+
return false;
26+
}
27+
Set<Integer> idxSet = m.get(val);
28+
int idx = idxSet.iterator().next();
29+
int lastIdx = l.size() - 1;
30+
l.set(idx, l.get(lastIdx));
31+
idxSet.remove(idx);
32+
33+
Set<Integer> lastIdxSet = m.get(l.get(lastIdx));
34+
lastIdxSet.remove(lastIdx);
35+
if (idx < lastIdx) {
36+
lastIdxSet.add(idx);
37+
}
38+
if (idxSet.isEmpty()) {
39+
m.remove(val);
40+
}
41+
l.remove(lastIdx);
42+
return true;
43+
}
44+
45+
/** Get a random element from the collection. */
46+
public int getRandom() {
47+
int size = l.size();
48+
return size == 0 ? -1 : l.get(rnd.nextInt(size));
49+
}
6150
}
6251

6352
/**

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