牛客网：NC116 把数字翻译成字符串

import java.util.*;
 
 
public class Solution {
    /**
     * 解码
     * @param nums string字符串 数字串
     * @return int整型
     */
    public int solve (String nums) {
        // write code here
        if (nums.charAt(0) == '0') return 0;
        if (nums == "10" || nums == "20") return 1;
        for (int i = 1; i < nums.length(); i++){
            if (nums.charAt(i) == '0' && (nums.charAt(i - 1) != '1' && nums.charAt(i - 1) != '2')) return 0;
        }
        int[] dp = new int[nums.length() + 1];
        Arrays.fill(dp, 1);
        for (int i = 2; i <= nums.length(); i++){
            if ((nums.charAt(i - 2) == '1' && nums.charAt(i - 1) != '0') || (nums.charAt(i - 2) == '2' && nums.charAt(i - 1) != '0' && nums.charAt(i - 1) < '7')){
                dp[i] = dp[i - 1] + dp[i - 2];
            } else{
                dp[i] = dp[i - 1];
            }
        }
        return dp[nums.length()];
    }
}