Algorithms—273.Integer to English Words

思路：拆成3位数一组进行拼接，考虑一下边界条件，写的比较冗余

public class Solution {
public String numberToWords(int num) {
if (num==0) {
return "Zero";
}
Map<String, String> map=new HashMap<String, String>();
map.put("1", "One");
map.put("2", "Two");
map.put("3", "Three");
map.put("4", "Four");
map.put("5", "Five");
map.put("6", "Six");
map.put("7", "Seven");
map.put("8", "Eight");
map.put("9", "Nine");
map.put("10", "Ten");
map.put("11", "Eleven");
map.put("12", "Twelve");
map.put("13", "Thirteen");
map.put("14", "Fourteen");
map.put("15", "Fifteen");
map.put("16", "Sixteen");
map.put("17", "Seventeen");
map.put("18", "Eighteen");
map.put("19", "Nineteen");
map.put("20", "Twenty");
map.put("30", "Thirty");
map.put("40", "Forty");
map.put("50", "Fifty");
map.put("60", "Sixty");
map.put("70", "Seventy");
map.put("80", "Eighty");
map.put("90", "Ninety");
String str=String.valueOf(num);
int length=str.length();
List<String> list=new ArrayList<String>();
while (str.length()>3) {
list.add(str.substring(length-3,length));
str=str.substring(0,length-3);
length=str.length();
}
list.add(str);
System.out.println("list.size()="+list.size());
List<String> ansList=new ArrayList<String>();
for (int i = 0; i < list.size(); i++) {
ansList.add(f(list.get(i),map));
}
String ans="";
if (ansList.size()!=0) {
ans=ansList.get(0);
ansList.remove(0);
}
if (ansList.size()!=0) {
if (ansList.get(0).length()!=0) {
if (ans.length()==0) {
ans=ansList.get(0)+" Thousand";
}else {
ans=ansList.get(0)+" Thousand "+ans;
}
}
ansList.remove(0);
}
if (ansList.size()!=0) {
if (ansList.get(0).length()!=0) {
if (ans.length()==0) {
ans=ansList.get(0)+" Million";
}else {
ans=ansList.get(0)+" Million "+ans;
}
}
ansList.remove(0);
}
if (ansList.size()!=0) {
if (ansList.get(0).length()!=0){
if (ans.length()==0) {
ans=ansList.get(0)+" Billion";
}else {
ans=ansList.get(0)+" Billion "+ans;
}
}
ansList.remove(0);
}
return ans;
}
public String f(String str,Map<String, String> map){
StringBuffer sb=new StringBuffer();
int i=Integer.parseInt(str);
if (i>=100) {
sb.append(map.get(""+i/100));
sb.append(" Hundred");
}
i=i%100;
if (i!=0) {
if (sb.length()!=0) {
sb.append(" ");
}
if (i%100<20) {
sb.append(map.get(""+i));
}else {
sb.append(map.get(""+(i-i%10)));
if (i%10!=0) {
sb.append(" ");
sb.append(map.get(""+i%10));
}
}
}
return sb.toString();
}
}

耗时：348ms。