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feat: add solutions to lc problem: No.0481
No.0481.Magical String
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‎solution/0400-0499/0481.Magical String/README.md

Lines changed: 88 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -45,22 +45,109 @@
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<!-- 这里可写通用的实现逻辑 -->
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**方法一：模拟**
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直接模拟字符串添加。
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时间复杂度 $O(n)$，空间复杂度 $O(n)$。
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<!-- tabs:start -->
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### **Python3**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```python
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class Solution:
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def magicalString(self, n: int) -> int:
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s = list('1221121')
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i = 5
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while len(s) < n:
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if s[i] == '1':
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s.append('2' if s[-1] == '1' else '1')
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else:
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s.extend(list('22' if s[-1] == '1' else '11'))
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i += 1
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return s[:n].count('1')
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```
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### **Java**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```java
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class Solution {
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public int magicalString(int n) {
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StringBuilder s = new StringBuilder("1221121");
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int i = 5;
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while (s.length() < n) {
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char c = s.charAt(s.length() - 1);
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if (s.charAt(i) == '1') {
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s.append(c == '1' ? '2' : '1');
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} else {
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s.append(c == '1' ? "22" : "11");
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}
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++i;
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}
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int ans = 0;
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for (i = 0; i < n; ++i) {
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if (s.charAt(i) == '1') {
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++ans;
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}
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}
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return ans;
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}
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}
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```
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### **C++**
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```cpp
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class Solution {
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public:
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int magicalString(int n) {
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string s = "1221121";
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int i = 5;
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while (s.size() < n) {
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if (s[i] == '1') {
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s += s.back() == '1' ? "2" : "1";
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} else {
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s += s.back() == '1' ? "22" : "11";
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}
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++i;
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}
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return count(s.begin(), s.begin() + n, '1');
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}
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};
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```
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### **Go**
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```go
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func magicalString(n int) int {
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s := []byte("1221121")
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i := 5
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for len(s) < n {
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c := s[len(s)-1]
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if s[i] == '1' {
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if c == '1' {
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s = append(s, '2')
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} else {
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s = append(s, '1')
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}
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} else {
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if c == '1' {
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s = append(s, '2')
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s = append(s, '2')
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} else {
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s = append(s, '1')
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s = append(s, '1')
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}
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}
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i++
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}
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return bytes.Count(s[:n], []byte("1"))
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}
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```
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### **...**

‎solution/0400-0499/0481.Magical String/README_EN.md

Lines changed: 82 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -44,13 +44,94 @@
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### **Python3**
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```python
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class Solution:
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def magicalString(self, n: int) -> int:
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s = list('1221121')
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i = 5
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while len(s) < n:
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if s[i] == '1':
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s.append('2' if s[-1] == '1' else '1')
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else:
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s.extend(list('22' if s[-1] == '1' else '11'))
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i += 1
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return s[:n].count('1')
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```
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### **Java**
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```java
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class Solution {
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public int magicalString(int n) {
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StringBuilder s = new StringBuilder("1221121");
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int i = 5;
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while (s.length() < n) {
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char c = s.charAt(s.length() - 1);
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if (s.charAt(i) == '1') {
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s.append(c == '1' ? '2' : '1');
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} else {
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s.append(c == '1' ? "22" : "11");
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}
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++i;
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}
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int ans = 0;
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for (i = 0; i < n; ++i) {
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if (s.charAt(i) == '1') {
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++ans;
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}
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}
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return ans;
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}
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}
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```
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### **C++**
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```cpp
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class Solution {
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public:
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int magicalString(int n) {
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string s = "1221121";
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int i = 5;
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while (s.size() < n) {
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if (s[i] == '1') {
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s += s.back() == '1' ? "2" : "1";
98+
} else {
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s += s.back() == '1' ? "22" : "11";
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}
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++i;
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}
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return count(s.begin(), s.begin() + n, '1');
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}
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};
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```
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### **Go**
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```go
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func magicalString(n int) int {
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s := []byte("1221121")
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i := 5
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for len(s) < n {
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c := s[len(s)-1]
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if s[i] == '1' {
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if c == '1' {
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s = append(s, '2')
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} else {
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s = append(s, '1')
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}
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} else {
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if c == '1' {
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s = append(s, '2')
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s = append(s, '2')
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} else {
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s = append(s, '1')
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s = append(s, '1')
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}
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}
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i++
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}
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return bytes.Count(s[:n], []byte("1"))
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}
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```
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### **...**

‎solution/0400-0499/0481.Magical String/Solution.cpp

Lines changed: 16 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,16 @@
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class Solution {
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public:
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int magicalString(int n) {
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string s = "1221121";
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int i = 5;
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while (s.size() < n) {
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if (s[i] == '1') {
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s += s.back() == '1' ? "2" : "1";
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} else {
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s += s.back() == '1' ? "22" : "11";
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}
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++i;
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}
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return count(s.begin(), s.begin() + n, '1');
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}
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};

‎solution/0400-0499/0481.Magical String/Solution.go

Lines changed: 24 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,24 @@
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func magicalString(n int) int {
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s := []byte("1221121")
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i := 5
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for len(s) < n {
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c := s[len(s)-1]
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if s[i] == '1' {
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if c == '1' {
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s = append(s, '2')
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} else {
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s = append(s, '1')
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}
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} else {
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if c == '1' {
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s = append(s, '2')
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s = append(s, '2')
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} else {
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s = append(s, '1')
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s = append(s, '1')
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}
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}
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i++
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}
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return bytes.Count(s[:n], []byte("1"))
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}

‎solution/0400-0499/0481.Magical String/Solution.java

Lines changed: 30 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,30 @@
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class Solution {
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public int magicalString(int n) {
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StringBuilder s = new StringBuilder("1221121");
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int i = 5;
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while (s.length() < n) {
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char c = s.charAt(s.length() - 1);
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if (s.charAt(i) == '1') {
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if (c == '1') {
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s.append('2');
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} else {
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s.append('1');
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}
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} else {
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if (c == '1') {
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s.append("22");
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} else {
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s.append("11");
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}
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}
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++i;
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}
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int ans = 0;
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for (i = 0; i < n; ++i) {
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if (s.charAt(i) == '1') {
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++ans;
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}
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}
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return ans;
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}
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}

‎solution/0400-0499/0481.Magical String/Solution.py

Lines changed: 11 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,11 @@
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class Solution:
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def magicalString(self, n: int) -> int:
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s = list('1221121')
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i = 5
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while len(s) < n:
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if s[i] == '1':
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s.append('2' if s[-1] == '1' else '1')
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else:
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s.extend(list('22' if s[-1] == '1' else '11'))
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i += 1
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return s[:n].count('1')

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