273. Integer to English Words

东西都放进去 然后取出来就好了

 

class Solution {
    public String numberToWords(int num) {
        if(num == 0) return "Zero";
        String res = "";
        String str = "" + num;
        String[] one = new String[]{"", "One ", "Two ", "Three ", "Four ", "Five ", "Six ", "Seven ", "Eight ", "Nine "};
        String[] two = new String[]{"", "", "Twenty ", "Thirty ", "Forty ", "Fifty ", "Sixty ", "Seventy ", "Eighty ", "Ninety "};
        String[] ten = new String[]{"Ten ", "Eleven ", "Twelve ", "Thirteen ", "Fourteen ", "Fifteen ", "Sixteen ", "Seventeen ", "Eighteen ", "Nineteen "};
        String[] three = new String[]{"", "One Hundred ", "Two Hundred ", "Three Hundred ", "Four Hundred ", "Five Hundred ", "Six Hundred ", "Seven Hundred ", "Eight Hundred ", "Nine Hundred "};
        int count = 0;
        for(int i = str.length()-1; i >= 0; i = i - 3){
            StringBuilder sb = new StringBuilder();
            String sub = str.substring(Math.max(0 , i-2), i+1);
            int temp = Integer.parseInt(sub);
            // System.out.println(temp);
            sb.append(three[temp/100]);
            temp = temp % 100;
            if(temp / 10 == 1){
                sb.append(ten[temp-10]);
            }else{
                 sb.append(two[temp/10]);
                 temp = temp%10;
                 sb.append(one[temp]);
            }
            if(sb.length() != 0 && count == 0){  //要是这个范围的数字不存在的话就不用加thousan million这些东西
                res = sb.toString() + res;
            }else if(sb.length() != 0 && count == 1){
                res = sb.toString() + "Thousand " + res;
            }else if(sb.length() != 0 && count == 2){
                res = sb.toString() + "Million " + res;
            }else if(sb.length() != 0 && count == 3){
                res = sb.toString() + "Billion " + res;
            }
            count++;
            
        }
        return res.trim();
        
    }
}