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Commit b9d8aab

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feat: add solutions to lc/lcof/lcci problems
lcci No.17.10.Find Majority Element lc No.0229.Majority Element II
1 parent 9a82099 commit b9d8aab

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-253
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21 files changed

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-253
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‎lcci/17.10.Find Majority Element/README.md‎

Lines changed: 82 additions & 33 deletions
Original file line numberDiff line numberDiff line change
@@ -37,6 +37,19 @@
3737

3838
摩尔投票法。时间复杂度 O(n),空间复杂度 O(1)。
3939

40+
一般而言,摩尔投票法需要对输入的列表进行**两次遍历**。在第一次遍历中,我们生成候选值 candidate,如果存在多数,那么该候选值就是多数值。在第二次遍历中,只需要简单地计算候选值的频率,以确认是否是多数值。
41+
42+
接下来我们详细看下**第一次遍历**:
43+
44+
我们需要两个变量:`cnt`, `candidate`,其中 `cnt` 初始化为 0,`candidate` 初始化可以是任何值,这里我们设置为 0。
45+
46+
对于列表中的每个元素 num,我们首先检查计数值 cnt,
47+
48+
- 若 `cnt == 0`,我们将候选值 candidate 设置为当前元素值,即 `candidate = num`。
49+
- 若 `candidate == num`,将 cnt 加 1,否则减 1。
50+
51+
**第二次遍历**,则是扫描列表中 candidate 出现的次数,若大于 `n/2`,则该候选值就是多数值,否则返回 -1。
52+
4053
<!-- tabs:start -->
4154

4255
### **Python3**
@@ -46,14 +59,12 @@
4659
```python
4760
class Solution:
4861
def majorityElement(self, nums: List[int]) -> int:
49-
cnt = major = 0
62+
cnt = candidate = 0
5063
for num in nums:
5164
if cnt == 0:
52-
major = num
53-
cnt = 1
54-
else:
55-
cnt += (1 if major == num else -1)
56-
return major
65+
candidate = num
66+
cnt += (1 if candidate == num else -1)
67+
return candidate if nums.count(candidate) > len(nums) / 2 else -1
5768
```
5869

5970
### **Java**
@@ -63,16 +74,20 @@ class Solution:
6374
```java
6475
class Solution {
6576
public int majorityElement(int[] nums) {
66-
int cnt = 0, major = 0;
77+
int cnt = 0, candidate = 0;
6778
for (int num : nums) {
6879
if (cnt == 0) {
69-
major = num;
70-
cnt = 1;
71-
} else {
72-
cnt += (major == num ? 1 : -1);
80+
candidate = num;
7381
}
82+
cnt += (num == candidate ? 1 : -1);
7483
}
75-
return major;
84+
cnt = 0;
85+
for (int num : nums) {
86+
if (num == candidate) {
87+
++cnt;
88+
}
89+
}
90+
return cnt > nums.length / 2 ? candidate : -1;
7691
}
7792
}
7893
```
@@ -86,16 +101,20 @@ class Solution {
86101
*/
87102
var majorityElement = function(nums) {
88103
let cnt = 0;
89-
let major = 0;
104+
let candidate = 0;
90105
for (const num of nums) {
91106
if (cnt == 0) {
92-
major = num;
93-
cnt = 1;
94-
} else {
95-
cnt += (major == num ? 1 : -1);
107+
candidate = num;
108+
}
109+
cnt += (candidate == num ? 1 : -1);
110+
}
111+
cnt = 0;
112+
for (const num of nums) {
113+
if (candidate == num) {
114+
++cnt;
96115
}
97116
}
98-
return major;
117+
return cnt >nums.length/2? candidate :-1;
99118
};
100119
```
101120

@@ -105,39 +124,69 @@ var majorityElement = function(nums) {
105124
class Solution {
106125
public:
107126
int majorityElement(vector<int>& nums) {
108-
int cnt = 0, major = 0;
109-
for (int num : nums) {
110-
if (cnt == 0) {
111-
major = num;
112-
cnt = 1;
113-
} else {
114-
cnt += (major == num ? 1 : -1);
115-
}
127+
int cnt = 0, candidate = 0;
128+
for (int num : nums)
129+
{
130+
if (cnt == 0) candidate = num;
131+
cnt += (candidate == num ? 1 : -1);
116132
}
117-
return major;
133+
cnt = count(nums.begin(), nums.end(), candidate);
134+
return cnt > nums.size() / 2 ? candidate : -1;
118135
}
119136
};
120137
```
121138
139+
### **Go**
140+
141+
```go
142+
func majorityElement(nums []int) int {
143+
var cnt, candidate int
144+
for _, num := range nums {
145+
if cnt == 0 {
146+
candidate = num
147+
}
148+
if candidate == num {
149+
cnt++
150+
} else {
151+
cnt--
152+
}
153+
}
154+
cnt = 0
155+
for _, num := range nums {
156+
if candidate == num {
157+
cnt++
158+
}
159+
}
160+
if cnt > len(nums)/2 {
161+
return candidate
162+
}
163+
return -1
164+
}
165+
```
166+
122167
### **C#**
123168

124169
```cs
125170
public class Solution {
126171
public int MajorityElement(int[] nums) {
127-
int cnt = 0, major = 0;
172+
int cnt = 0, candidate = 0;
128173
foreach (int num in nums)
129174
{
130175
if (cnt == 0)
131176
{
132-
major = num;
133-
cnt = 1;
177+
candidate = num;
134178
}
135-
else
179+
cnt += (candidate == num ? 1 : -1);
180+
}
181+
cnt = 0;
182+
foreach (int num in nums)
183+
{
184+
if (candidate == num)
136185
{
137-
cnt += (major == num ? 1 : -1);
186+
++cnt;
138187
}
139188
}
140-
return major;
189+
return cnt>nums.Length/2?candidate:-1;
141190
}
142191
}
143192
```

‎lcci/17.10.Find Majority Element/README_EN.md‎

Lines changed: 69 additions & 33 deletions
Original file line numberDiff line numberDiff line change
@@ -47,31 +47,33 @@ Boyer–Moore majority vote algorithm
4747
```python
4848
class Solution:
4949
def majorityElement(self, nums: List[int]) -> int:
50-
cnt = major = 0
50+
cnt = candidate = 0
5151
for num in nums:
5252
if cnt == 0:
53-
major = num
54-
cnt = 1
55-
else:
56-
cnt += (1 if major == num else -1)
57-
return major
53+
candidate = num
54+
cnt += (1 if candidate == num else -1)
55+
return candidate if nums.count(candidate) > len(nums) / 2 else -1
5856
```
5957

6058
### **Java**
6159

6260
```java
6361
class Solution {
6462
public int majorityElement(int[] nums) {
65-
int cnt = 0, major = 0;
63+
int cnt = 0, candidate = 0;
6664
for (int num : nums) {
6765
if (cnt == 0) {
68-
major = num;
69-
cnt = 1;
70-
} else {
71-
cnt += (major == num ? 1 : -1);
66+
candidate = num;
7267
}
68+
cnt += (num == candidate ? 1 : -1);
7369
}
74-
return major;
70+
cnt = 0;
71+
for (int num : nums) {
72+
if (num == candidate) {
73+
++cnt;
74+
}
75+
}
76+
return cnt > nums.length / 2 ? candidate : -1;
7577
}
7678
}
7779
```
@@ -85,16 +87,20 @@ class Solution {
8587
*/
8688
var majorityElement = function(nums) {
8789
let cnt = 0;
88-
let major = 0;
90+
let candidate = 0;
8991
for (const num of nums) {
9092
if (cnt == 0) {
91-
major = num;
92-
cnt = 1;
93-
} else {
94-
cnt += (major == num ? 1 : -1);
93+
candidate = num;
94+
}
95+
cnt += (candidate == num ? 1 : -1);
96+
}
97+
cnt = 0;
98+
for (const num of nums) {
99+
if (candidate == num) {
100+
++cnt;
95101
}
96102
}
97-
return major;
103+
return cnt >nums.length/2? candidate :-1;
98104
};
99105
```
100106

@@ -104,39 +110,69 @@ var majorityElement = function(nums) {
104110
class Solution {
105111
public:
106112
int majorityElement(vector<int>& nums) {
107-
int cnt = 0, major = 0;
108-
for (int num : nums) {
109-
if (cnt == 0) {
110-
major = num;
111-
cnt = 1;
112-
} else {
113-
cnt += (major == num ? 1 : -1);
114-
}
113+
int cnt = 0, candidate = 0;
114+
for (int num : nums)
115+
{
116+
if (cnt == 0) candidate = num;
117+
cnt += (candidate == num ? 1 : -1);
115118
}
116-
return major;
119+
cnt = count(nums.begin(), nums.end(), candidate);
120+
return cnt > nums.size() / 2 ? candidate : -1;
117121
}
118122
};
119123
```
120124
125+
### **Go**
126+
127+
```go
128+
func majorityElement(nums []int) int {
129+
var cnt, candidate int
130+
for _, num := range nums {
131+
if cnt == 0 {
132+
candidate = num
133+
}
134+
if candidate == num {
135+
cnt++
136+
} else {
137+
cnt--
138+
}
139+
}
140+
cnt = 0
141+
for _, num := range nums {
142+
if candidate == num {
143+
cnt++
144+
}
145+
}
146+
if cnt > len(nums)/2 {
147+
return candidate
148+
}
149+
return -1
150+
}
151+
```
152+
121153
### **C#**
122154

123155
```cs
124156
public class Solution {
125157
public int MajorityElement(int[] nums) {
126-
int cnt = 0, major = 0;
158+
int cnt = 0, candidate = 0;
127159
foreach (int num in nums)
128160
{
129161
if (cnt == 0)
130162
{
131-
major = num;
132-
cnt = 1;
163+
candidate = num;
133164
}
134-
else
165+
cnt += (candidate == num ? 1 : -1);
166+
}
167+
cnt = 0;
168+
foreach (int num in nums)
169+
{
170+
if (candidate == num)
135171
{
136-
cnt += (major == num ? 1 : -1);
172+
++cnt;
137173
}
138174
}
139-
return major;
175+
return cnt>nums.Length/2?candidate:-1;
140176
}
141177
}
142178
```
Lines changed: 7 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -1,15 +1,13 @@
11
class Solution {
22
public:
33
int majorityElement(vector<int>& nums) {
4-
int cnt = 0, major = 0;
5-
for (int num : nums) {
6-
if (cnt == 0) {
7-
major = num;
8-
cnt = 1;
9-
} else {
10-
cnt += (major == num ? 1 : -1);
11-
}
4+
int cnt = 0, candidate = 0;
5+
for (int num : nums)
6+
{
7+
if (cnt == 0) candidate = num;
8+
cnt += (candidate == num ? 1 : -1);
129
}
13-
return major;
10+
cnt = count(nums.begin(), nums.end(), candidate);
11+
return cnt > nums.size() / 2 ? candidate : -1;
1412
}
1513
};
Lines changed: 10 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -1,18 +1,22 @@
11
public class Solution {
22
public int MajorityElement(int[] nums) {
3-
int cnt = 0, major = 0;
3+
int cnt = 0, candidate = 0;
44
foreach (int num in nums)
55
{
66
if (cnt == 0)
77
{
8-
major = num;
9-
cnt = 1;
8+
candidate = num;
109
}
11-
else
10+
cnt += (candidate == num ? 1 : -1);
11+
}
12+
cnt = 0;
13+
foreach (int num in nums)
14+
{
15+
if (candidate == num)
1216
{
13-
cnt+=(major==num?1:-1);
17+
++cnt;
1418
}
1519
}
16-
return major;
20+
return cnt>nums.Length/2?candidate:-1;
1721
}
1822
}

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