273. 整数转换英文表示
使用了模拟的方法，最多10位 从左边开始 1-3位为百位处理模块 4-6 位为千位处理 7位为百万位处理在这里我发现了规律，每一段都需要处理一个 百位数，那么问题就缩小到翻译 1-999 和拼接字符串的问题了。
这道题考察工业代码的开发能力。拆解成多个子方法开发就会简编很多。我使用basicNum()方法为内核，其余问题就变成了简单的字符串拼接。
1025666 输出 "One Million Twenty Five Thousand Six Hundred Sixty Six" 预期结果 "One Million Twenty Five Thousand Six Hundred Sixty Six"
执行用时：2 ms, 在所有 Java 提交中击败了92.33%的用户
内存消耗：37.8 MB, 在所有 Java 提交中击败了60.00%的用户
class Solution {
String[] ten_strs = {"Zero","One","Two","Three","Four","Five","Six","Seven","Eight","Nine"};//9
String[] twenty_strs = {"Ten","Eleven","Twelve","Thirteen","Fourteen","Fifteen","Sixteen","Seventeen","Eighteen","Nineteen"};//10
String[] ninety_strs = {"Twenty","Thirty","Forty","Fifty","Sixty","Seventy","Eighty","Ninety"};//8
final int billion = 1000000000;
final int million = 1000000;
final int thousand = 1000;
StringBuilder sb;
public String numberToWords(int num) {
sb = new StringBuilder();
if(num >= billion){
sb.append(billion_part(num));
}
if(num>=million){
String million_part= million_part(num);
if(!million_part.equals("")&&sb.toString().length()!=0) sb.append(" ");
sb.append(million_part);
}
if(num>=thousand){
String thousand_part=thousand_part(num);
if(!thousand_part.equals("")&&sb.toString().length()!=0) sb.append(" ");
sb.append(thousand_part);
}
//处理千位以下的数
String hundred_str = basicNum(num);
// &&!hundred_str.equals("Zero")
if(!hundred_str.equals("")){
if(hundred_str.equals("Zero")&&sb.toString().length()!=0){
}else{
if(sb.toString().length()!=0&&!hundred_str.equals(" ")) sb.append(" ");
sb.append(hundred_str);
}
}
//if(sb.length()>0&&sb.toString().charAt(sb.length()-1)!=' ')sb.deleteCharAt(sb.length()-1);
return sb.toString();
}
public String billion_part(int num){
num = num/billion;
StringBuilder sb = new StringBuilder();
sb.append(basicNum(num));
sb.append(" ");
sb.append("Billion");
return sb.toString();
}
// 百万级处理方法 为什么1000010会出现额外的空格
public String million_part(int num){
num = (num%billion)/million;
StringBuilder sb = new StringBuilder();
if(num!=0){
sb.append(basicNum(num));
sb.append(" ");
sb.append("Million");
}
return sb.toString();
}
public String thousand_part(int num){
num = (num%million)/1000;
StringBuilder sb = new StringBuilder();
if(num!=0){
sb.append(basicNum(num));
sb.append(" ");
sb.append("Thousand");
}
return sb.toString();
}
public String basicNum(int num){
if(num == 0) return "Zero";
num = num%1000;
if(num == 0) return "";
// 边界条件
if(num == 0&&this.sb.toString().length()==0) return "Zero";
if(num<10) return ten_strs[num];
//Hundred
StringBuilder sb= new StringBuilder();
int high = num/100;
if(high!=0){
sb.append(ten_strs[high]);
sb.append(" ");
sb.append("Hundred");
}
// mid代表了十 位
int mid = (num%100)/10;
// low 代表了个位
int low = (num%100)%10;
//当 20<=num<=99 时 应该调用 20-90 并且加上 1-9
if(mid!=1&&mid!=0){
// 这里出现了符号问题 “ ”
if(sb.toString().length()!=0){
sb.append(" ");
}
sb.append(ninety_strs[mid-2]);
if(low!=0){
if(sb.toString().length()!=0)sb.append(" ");
sb.append(ten_strs[low]);
}
}else if(mid==1){ //范围在10-19
if(sb.toString().length()!=0)sb.append(" ");
sb.append(twenty_strs[low]);
}else if(mid ==0&& low!=0){ //范围在1到 9
String lastnum = ten_strs[low];
if(!lastnum.equals("Zero")){
if(sb.toString().length()!=0)sb.append(" ");
sb.append(ten_strs[low]);
}
}
return sb.toString();
}
}
