共计 3294 个字符，预计需要花费 9 分钟才能阅读完成。
题目要求
Given a non-empty string containing an out-of-order English representation of digits 0-9, output the digits in ascending order.
Note:
Input contains only lowercase English letters.
Input is guaranteed to be valid and can be transformed to its original digits. That means invalid inputs such as “abc” or “zerone” are not permitted.
Input length is less than 50,000.
Example 1:
Input: “owoztneoer”
Output: “012”
Example 2:
Input: “fviefuro”
Output: “45”
一个非空的英文字符串，其中包含着乱序的阿拉伯数字的英文单词。如 012 对应的英文表达为 zeroonetwo 并继续乱序成 owoztneoer。要求输入乱序的英文表达式，找出其中包含的所有 0 - 9 的数字，并按照从小到大输出。
思路和代码
首先将数字和英文表示列出来：
0 zero
1 one
2 two
3 three
4 four
5 five
6 six
7 seven
8 eight
9 nine
粗略一看，我们知道有许多字母只在一个英文数字中出现，比如 z 只出现在 zero 中。因此对于这种字母，它一旦出现，就意味着该数字一定出现了。因此一轮过滤后可以得出只出现一次的字母如下：
0 zero -> z
1 one
2 two -> w
3 three
4 four -> u
5 five
6 six -> x
7 seven
8 eight
9 nine
再对剩下的数字字母过滤出只出现一次的字母：
1 one
3 three -> r
5 five -> f
7 seven -> s
8 eight -> g
9 nine
最后对 one 和 nine 分别用 o 和 i 进行区分即可。因此可以得出如下代码：
public String originalDigits(String s) {
int[] letterCount = new int[26];
for(char c : s.toCharArray()) {
letterCount[c-‘a’]++;
}
int[] result = new int[10];
//zero
if((result[2] = letterCount[‘z’-‘a’]) != 0) {
result[0] = letterCount[‘z’ – ‘a’];
letterCount[‘z’-‘a’] = 0;
letterCount[‘e’-‘a’] -= result[0];
letterCount[‘r’-‘a’] -= result[0];
letterCount[‘o’-‘a’] -= result[0];
}
//two
if((result[2] = letterCount[‘w’-‘a’]) != 0) {
letterCount[‘t’-‘a’] -= result[2];
letterCount[‘w’-‘a’] = 0;
letterCount[‘o’-‘a’] -= result[2];
}
//four
if((result[4] = letterCount[‘u’-‘a’]) != 0) {
letterCount[‘f’-‘a’] -= result[4];
letterCount[‘o’-‘a’] -= result[4];
letterCount[‘u’-‘a’] -= result[4];
letterCount[‘r’-‘a’] -= result[4];
}
//five
if((result[5] = letterCount[‘f’-‘a’]) != 0) {
letterCount[‘f’-‘a’] -= result[5];
letterCount[‘i’-‘a’] -= result[5];
letterCount[‘v’-‘a’] -= result[5];
letterCount[‘e’-‘a’] -= result[5];
}
//six
if((result[6] = letterCount[‘x’-‘a’]) != 0) {
letterCount[‘s’-‘a’] -= result[6];
letterCount[‘i’-‘a’] -= result[6];
letterCount[‘x’-‘a’] -= result[6];
}
//seven
if((result[7] = letterCount[‘s’-‘a’]) != 0) {
letterCount[‘s’-‘a’] -= result[7];
letterCount[‘e’-‘a’] -= result[7] * 2;
letterCount[‘v’-‘a’] -= result[7];
letterCount[‘n’-‘a’] -= result[7];
}
//one
if((result[1] = letterCount[‘o’-‘a’]) != 0) {
letterCount[‘o’-‘a’] -= result[1];
letterCount[‘n’-‘a’] -= result[1];
letterCount[‘e’-‘a’] -= result[1];
}
//eight
if((result[8] = letterCount[‘g’-‘a’]) != 0) {
letterCount[‘e’-‘a’] -= result[8];
letterCount[‘i’-‘a’] -= result[8];
letterCount[‘g’-‘a’] -= result[8];
letterCount[‘h’-‘a’] -= result[8];
letterCount[‘t’-‘a’] -= result[8];
}
//nine
if((result[9] = letterCount[‘i’-‘a’]) != 0) {
letterCount[‘n’-‘a’] -= result[9] * 2;
letterCount[‘i’-‘a’] -= result[9];
letterCount[‘e’-‘a’] -= result[9];
}
result[3] = letterCount[‘t’-‘a’];
StringBuilder sb = new StringBuilder();
for(int i = 0 ; i<result.length ; i++) {
for(int j = 0 ; j<result[i] ; j++) {
sb.append(i);
}
}
return sb.toString();
}
上面的代码未免写的太繁琐了，对其进一步优化可以得到如下代码：
public String originalDigits2(String s) {
int[] alphabets = new int[26];
for (char ch : s.toCharArray()) {
alphabets[ch – ‘a’] += 1;
}
int[] digits = new int[10];
digits[0] = alphabets[‘z’ – ‘a’];
digits[2] = alphabets[‘w’ – ‘a’];
digits[6] = alphabets[‘x’ – ‘a’];
digits[8] = alphabets[‘g’ – ‘a’];
digits[7] = alphabets[‘s’ – ‘a’] – digits[6];
digits[5] = alphabets[‘v’ – ‘a’] – digits[7];
digits[3] = alphabets[‘h’ – ‘a’] – digits[8];
digits[4] = alphabets[‘f’ – ‘a’] – digits[5];
digits[9] = alphabets[‘i’ – ‘a’] – digits[6] – digits[8] – digits[5];
digits[1] = alphabets[‘o’ – ‘a’] – digits[0] – digits[2] – digits[4];
StringBuilder sb = new StringBuilder();
for (int d = 0; d < 10; d++) {
for (int count = 0; count < digits[d]; count++) sb.append(d);
}
return sb.toString();
}