46 lines
1.0 KiB
Java
46 lines
1.0 KiB
Java
# 58.2 左旋转字符串
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## 题目链接
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[牛客网](https://www.nowcoder.com/practice/12d959b108cb42b1ab72cef4d36af5ec?tpId=13&tqId=11196&tPage=1&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking&from=cyc_github)
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## 题目描述
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将字符串 S 从第 K 位置分隔成两个子字符串，并交换这两个子字符串的位置。
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```html
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Input:
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S="abcXYZdef"
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K=3
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Output:
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"XYZdefabc"
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```
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## 解题思路
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先将 "abc" 和 "XYZdef" 分别翻转，得到 "cbafedZYX"，然后再把整个字符串翻转得到 "XYZdefabc"。
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```java
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public String LeftRotateString(String str, int n) {
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if (n >= str.length())
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return str;
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char[] chars = str.toCharArray();
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reverse(chars, 0, n - 1);
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reverse(chars, n, chars.length - 1);
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reverse(chars, 0, chars.length - 1);
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return new String(chars);
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}
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private void reverse(char[] chars, int i, int j) {
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while (i < j)
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swap(chars, i++, j--);
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}
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private void swap(char[] chars, int i, int j) {
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char t = chars[i];
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chars[i] = chars[j];
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chars[j] = t;
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}
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```
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