48 lines
1.5 KiB
Java
48 lines
1.5 KiB
Java
# 38. 字符串的排列
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[NowCoder](https://www.nowcoder.com/practice/fe6b651b66ae47d7acce78ffdd9a96c7?tpId=13&tqId=11180&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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输入一个字符串，按字典序打印出该字符串中字符的所有排列。例如输入字符串 abc，则打印出由字符 a, b, c 所能排列出来的所有字符串 abc, acb, bac, bca, cab 和 cba。
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## 解题思路
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```java
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private ArrayList<String> ret = new ArrayList<>();
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public ArrayList<String> Permutation(String str) {
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if (str.length() == 0)
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return ret;
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char[] chars = str.toCharArray();
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Arrays.sort(chars);
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backtracking(chars, new boolean[chars.length], new StringBuilder());
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return ret;
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}
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private void backtracking(char[] chars, boolean[] hasUsed, StringBuilder s) {
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if (s.length() == chars.length) {
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ret.add(s.toString());
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return;
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}
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for (int i = 0; i < chars.length; i++) {
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if (hasUsed[i])
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continue;
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if (i != 0 && chars[i] == chars[i - 1] && !hasUsed[i - 1]) /* 保证不重复 */
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continue;
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hasUsed[i] = true;
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s.append(chars[i]);
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backtracking(chars, hasUsed, s);
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s.deleteCharAt(s.length() - 1);
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hasUsed[i] = false;
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}
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}
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```
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