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

---
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);
    }
}
```

[Offer 58 - I. 翻转单词顺序](https://leetcode-cn.com/problems/fan-zhuan-dan-ci-shun-xu-lcof/)

```java
class Solution {

    public String reverseWords(String s) {
        String[] strings = s.trim().split(" ");
        StringBuilder sb = new StringBuilder();
        for (int i = strings.length - 1; i >= 0; i--) {
            if (strings[i].equals("")) {
                continue;
            }
            sb.append(strings[i]).append(" ");
        }
        return sb.toString().trim();
    }
}
```