JZ-071 - translate numbers into strings

translate numbers to strings

Topic description

Given a number, translate it into a string according to the following rules: 1 translates to "a", 2 translates to "b"... 26 translates to "z". There are many possible translations for a number. For example, 12258 has 5 kinds, which are abbeh, lbeh, aveh, abyh, and lyh. Implement a function that counts how many different translation methods a number has.

title link : [translate numbers into strings]()

code

/**
 * 标题：把数字翻译成字符串
 * 题目描述
 * 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。
 */
public class Jz71 {

    /**
     * 动态规划
     *
     * @param s
     * @return
     */
    public int numDecodings(String s) {
        if (s == null || s.length() == 0) {
            return 0;
        }
        int n = s.length();
        int[] dp = new int[n + 1];
        dp[0] = 1;
        dp[1] = s.charAt(0) == '0' ? 0 : 1;
        for (int i = 2; i <= n; i++) {
            int one = Integer.valueOf(s.substring(i - 1, i));
            if (one != 0) {
                dp[i] += dp[i - 1];
            }
            if (s.charAt(i - 2) == '0') {
                continue;
            }
            int two = Integer.valueOf(s.substring(i - 2, i));
            if (two <= 26) {
                dp[i] += dp[i - 2];
            }
        }
        return dp[n];
    }

    public static void main(String[] args) {
        Jz71 jz71 = new Jz71();
        System.out.println(jz71.numDecodings("12258"));
    }
}

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