昨天晚上参加baidu笔试的2个题目，大家讨论一下：
1.序列Seq=[a,b,…z,aa,ab…az,ba,bb,…bz,…,za,zb,…zz,aaa,…] 类似与excel的排列，任意给出一个字符串s=[a-z]+(由a-z字符组成的任意长度字符串），请问s是序列Seq的第几个。
2.需求：需要引入用户对搜索结果相关性的评分100分制，希望用户的打分能帮助搜索引擎排序，但又要避免恶意投票，作弊等，请设计一个比较公平的评分系统。
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第一题，相当于26进制嘛，
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- Java code
public class Test1 { public static void main(String[] args) { int n = letter2Number("abc"); System.out.println(n); } public static int letter2Number(String letters) { if(!letters.matches("[a-zA-Z]+")) { throw new IllegalArgumentException("Format ERROR!"); } char[] chs = letters.toLowerCase().toCharArray(); int result = 0; for(int i = chs.length - 1, p = 1; i >= 0; i--) { result += getNum(chs[i]) * p; p *= 26; } return result; } private static int getNum(char c) { return c - 'a' + 1; }}
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- Java code
String str = "abcdefghijklmnopqrstuvwxyz"; public int getNum(String oneChar){//传一个字母 return str.indexOf(oneChar)+1; } public int q26(int a){ if(a==0){ return 1; } else if(a==1){ return 26; } else{ return 26*q26(a-1); } } public int changeToNum(String moreChar){//传的是一个字符串 int all = 0; int p = 0; char[] newOne = moreChar.toCharArray(); //挨个字母换成十进制数，然后再运算 for(int i = 0 ;i <newOne.length ; i++){ String tag = Character.toString(newOne[i]); int num = getNum(tag); all = all + num*q26(newOne.length-i-1); } return all; }
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那么麻烦?
JDK里面就有了,一句话:
ava.lang.Integer.parseInt(String "abc", 26);
int java.lang.Integer.parseInt(String s, int radix) throws NumberFormatException
Parses the string argument as a signed integer in the radix specified by the second argument. The characters in the string must all be digits of the specified radix (as determined by whether java.lang.Character.digit(char, int) returns a nonnegative value), except that the first character may be an ASCII minus sign '-' ('\u002D') to indicate a negative value. The resulting integer value is returned.
An exception of type NumberFormatException is thrown if any of the following situations occurs:
The first argument is null or is a string of length zero.
The radix is either smaller than java.lang.Character.MIN_RADIX or larger than java.lang.Character.MAX_RADIX.
Any character of the string is not a digit of the specified radix, except that the first character may be a minus sign '-' ('\u002D') provided that the string is longer than length 1.
The value represented by the string is not a value of type int.
Examples:
parseInt("0", 10) returns 0
parseInt("473", 10) returns 473
parseInt("-0", 10) returns 0
parseInt("-FF", 16) returns -255
parseInt("1100110", 2) returns 102
parseInt("2147483647", 10) returns 2147483647
parseInt("-2147483648", 10) returns -2147483648
parseInt("2147483648", 10) throws a NumberFormatException
parseInt("99", 8) throws a NumberFormatException
parseInt("Kona", 10) throws a NumberFormatException
parseInt("Kona", 27) returns 411787