32 lines
1015 B
Java
32 lines
1015 B
Java
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# 46. 把数字翻译成字符串
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[Leetcode](https://leetcode.com/problems/decode-ways/description/)
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## 题目描述
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给定一个数字，按照如下规则翻译成字符串：1 翻译成“a”，2 翻译成“b”... 26 翻译成“z”。一个数字有多种翻译可能，例如 12258 一共有 5 种，分别是 abbeh，lbeh，aveh，abyh，lyh。实现一个函数，用来计算一个数字有多少种不同的翻译方法。
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## 解题思路
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```java
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public int numDecodings(String s) {
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if (s == null || s.length() == 0)
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return 0;
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int n = s.length();
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int[] dp = new int[n + 1];
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dp[0] = 1;
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dp[1] = s.charAt(0) == '0' ? 0 : 1;
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for (int i = 2; i <= n; i++) {
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int one = Integer.valueOf(s.substring(i - 1, i));
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if (one != 0)
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dp[i] += dp[i - 1];
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if (s.charAt(i - 2) == '0')
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continue;
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int two = Integer.valueOf(s.substring(i - 2, i));
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if (two <= 26)
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dp[i] += dp[i - 2];
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}
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return dp[n];
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}
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```
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