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| 1 | +/* |
| 2 | + * @lc app=leetcode.cn id=394 lang=java |
| 3 | + * |
| 4 | + * [394] 字符串解码 |
| 5 | + * |
| 6 | + * https://leetcode-cn.com/problems/decode-string/description/ |
| 7 | + * |
| 8 | + * algorithms |
| 9 | + * Medium (50.12%) |
| 10 | + * Likes: 372 |
| 11 | + * Dislikes: 0 |
| 12 | + * Total Accepted: 46.4K |
| 13 | + * Total Submissions: 87.9K |
| 14 | + * Testcase Example: '"3[a]2[bc]"' |
| 15 | + * |
| 16 | + * 给定一个经过编码的字符串,返回它解码后的字符串。 |
| 17 | + * |
| 18 | + * 编码规则为: k[encoded_string],表示其中方括号内部的 encoded_string 正好重复 k 次。注意 k 保证为正整数。 |
| 19 | + * |
| 20 | + * 你可以认为输入字符串总是有效的;输入字符串中没有额外的空格,且输入的方括号总是符合格式要求的。 |
| 21 | + * |
| 22 | + * 此外,你可以认为原始数据不包含数字,所有的数字只表示重复的次数 k ,例如不会出现像 3a 或 2[4] 的输入。 |
| 23 | + * |
| 24 | + * |
| 25 | + * |
| 26 | + * 示例 1: |
| 27 | + * |
| 28 | + * 输入:s = "3[a]2[bc]" |
| 29 | + * 输出:"aaabcbc" |
| 30 | + * |
| 31 | + * |
| 32 | + * 示例 2: |
| 33 | + * |
| 34 | + * 输入:s = "3[a2[c]]" |
| 35 | + * 输出:"accaccacc" |
| 36 | + * |
| 37 | + * |
| 38 | + * 示例 3: |
| 39 | + * |
| 40 | + * 输入:s = "2[abc]3[cd]ef" |
| 41 | + * 输出:"abcabccdcdcdef" |
| 42 | + * |
| 43 | + * |
| 44 | + * 示例 4: |
| 45 | + * |
| 46 | + * 输入:s = "abc3[cd]xyz" |
| 47 | + * 输出:"abccdcdcdxyz" |
| 48 | + * |
| 49 | + * |
| 50 | + */ |
| 51 | + |
| 52 | +// @lc code=start |
| 53 | +class Solution { |
| 54 | + |
| 55 | + int index = 0; |
| 56 | + |
| 57 | + public String decodeString(String s) { |
| 58 | + int len = s.length(); |
| 59 | + int num = 0; |
| 60 | + StringBuilder sb = new StringBuilder(); |
| 61 | + |
| 62 | + while (index < len) { |
| 63 | + char ch = s.charAt(index++); |
| 64 | + if ('0' <= ch && ch <= '9') { |
| 65 | + num = num * 10 + (ch - '0'); |
| 66 | + } else if (ch == '[') { |
| 67 | + String temp = decodeString(s); |
| 68 | + for (int j = 0; j < num; j++) { |
| 69 | + sb.append(temp); |
| 70 | + } |
| 71 | + num = 0; |
| 72 | + } else if (ch == ']') { |
| 73 | + return sb.toString(); |
| 74 | + } else { |
| 75 | + sb.append(ch); |
| 76 | + } |
| 77 | + } |
| 78 | + |
| 79 | + return sb.toString(); |
| 80 | + } |
| 81 | +} |
| 82 | +// @lc code=end |
| 83 | + |
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