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LetterConvert.java
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88 lines (62 loc) · 1.59 KB
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public class LetterConvert{
public static int letterConvert1(char[] arr){
return process(arr,0);
}
public static int process(char[] arr,int index){
//因为已经遍历了整个数组，说明全部都可以转换成功
if(index== arr.length) return 1;
if(arr[index]=='0'){
return 0;
}
int p1 = process(arr,index+1);
int p2=0;
if(index+1 < arr.length && (arr[index]-'0')*10 + arr[index+1]-'0' < 27){
p2= process(arr,index+2);
}
return p1+p2;
}
public static int letterConvert2(char[] arr){
int[] dp=new int[arr.length];
for (int i=0; i<dp.length;i++ ) {
dp[i]=-1;
}
return process(arr,0);
}
public static int process2(char[] arr,int index,int[] dp){
if(dp[index] !=-1)
return dp[index];
//因为已经遍历了整个数组，说明全部都可以转换成功
if(index== arr.length)
return 1;
if(arr[index]=='0'){
return 0;
}
int p1 = process2(arr,index+1,dp);
int p2=0;
if(index+1 < arr.length && (arr[index]-'0')*10 + arr[index+1]-'0' < 27){
p2= process2(arr,index+2,dp);
}
dp[index]= p1+p2;
return p1+p2;
}
public static int letterConvert3(char[] arr){
int N = arr.length;
int[] dp=new int[N+1];
dp[N]=1;
for (int index=N-1; index>=0; index--) {
if(arr[index]!='0'){
int p1 = dp[index+1];
int p2=0;
if(index+1 < arr.length && (arr[index]-'0')*10 + arr[index+1]-'0' < 27){
p2= dp[index+2];
}
dp[index]= p1+p2;
}
}
return dp[0];
}
public static void main(String[] args){
char[] arr ="22333410".toCharArray();
System.out.println("count = "+ letterConvert1(arr));
}
}