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NumDecodings.java
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31 lines (29 loc) · 882 Bytes
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package dynamic;
public class NumDecodings {
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' ? 1 : 0;
for (int i = 2; i <=n ; i++) {
int first = Integer.valueOf(s.substring(i-1,i));
int second = Integer.valueOf(s.substring(i-2,i));
if (first >= 1 && first <=9){
dp[i] += dp[i-1];
}
if (second >= 10 && second <= 26){
dp[i] += dp[i-2];
}
}
return dp[n];
}
public static void main(String[] args) {
String s = "226";
NumDecodings numDecodings = new NumDecodings();
int r = numDecodings.numDecodings(s);
System.out.println(r);
}
}