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android-notes/blogs/Algorithm/剑指 Offer/字符串相关.md

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---
字符串相关
---
[05. 替换空格](https://leetcode-cn.com/problems/ti-huan-kong-ge-lcof/)
```java
class Solution {
public String replaceSpace(String s) {
StringBuilder builder = new StringBuilder();
int i = 0;
while (i < s.length()) {
char c = s.charAt(i);
if (c == ' ') {
builder.append("%20");
} else {
builder.append(c);
}
i++;
}
return builder.toString();
}
}
```
[50. 第一个只出现一次的字符](https://leetcode-cn.com/problems/di-yi-ge-zhi-chu-xian-yi-ci-de-zi-fu-lcof/)
```java
class Solution {
public char firstUniqChar(String s) {
if (s.length() == 0) {
return ' ';
}
LinkedHashMap<Character, Integer> map = new LinkedHashMap<>();
for (char c : s.toCharArray()) {
map.put(c, map.getOrDefault(c, 0) + 1);
}
for (Map.Entry<Character, Integer> entry : map.entrySet()) {
if (entry.getValue() == 1) {
return entry.getKey();
}
}
return ' ';
}
}
```
```java
class Solution {
public char firstUniqChar(String s) {
char[] array = s.toCharArray();
int[] ints = new int[256];
for (char c : array) {
ints[c]++;
}
for (char c : array) {
if (ints[c] == 1) {
return c;
}
}
return ' ';
}
}
```
[58 - II. 左旋转字符串](https://leetcode-cn.com/problems/zuo-xuan-zhuan-zi-fu-chuan-lcof/)
```java
class Solution {
public String reverseLeftWords(String s, int n) {
return s.substring(n) + s.substring(0, n);
}
}
```