PIE Chapter 6--Java代码

【程序员面试攻略】一书中的第六章代码：

import java.util.Hashtable;import java.lang.StringBuffer;public class Ch6 {/* * find the first non-repeated character in one string * Input: one string * Output: the first non-repeated character */ public Character firstNonRepeated(String str){int length = str.length();Character ch;Integer intgr = null; Hashtable<Character, Integer> charHash = new Hashtable<Character, Integer>();Integer numOne = new Integer(1);Integer numMoreThanOne = new Integer(2);//get all the character from the stringfor(int i = 0; i < length; i++){ch = new Character(str.charAt(i));intgr = (Integer) charHash.get(ch);if(intgr == null)charHash.put(ch, numOne);elsecharHash.put(ch, numMoreThanOne);}//check for the first non-rep char from the hashtablefor (int i = 0; i < length; i++){ch = new Character(str.charAt(i));intgr = (Integer) charHash.get(ch);if(intgr == numOne)return ch;}return null;} /* * remove all the chars from a string  * input: string str, and the string needs to be removed * output: new string without the chars */public String removeChars(String str, String remove){StringBuffer sb = new StringBuffer();for(char c : str.toCharArray()){if(remove.indexOf(c) == -1) sb.append(c);}return sb.toString();}public String removeChar(String str, String remove){char[] s = str.toCharArray();char[] r = remove.toCharArray();boolean[] flags = new boolean[128];int len = s.length;int src, dst;for(src = 0; src < r.length; ++src){flags[r[src]] = true;}src = 0;dst = 0; while(src < len){//for(src = 0, dst = 0; src < len; ++src){if( !flags[s[src]]){s[dst++] = s[src];}++src;}return new String(s,0,dst);}/* * revert a given string. * input: a string: Do or do not, there is no try. * output: a reverted string: try. no is there not, do or Do * the idea is to get each words in order, and output them reversely. * we can do it by StringBuffer or Stack. */public String revertString(String str){StringBuffer sb = new StringBuffer();String[] sa = str.split(" ");for(int i = sa.length -1; i >= 0; --i ){sb.append(sa[i].toString() + " ");}return sb.toString();}/* * Another way to do reverseString:  * The idea is to get the whole string reversely, * and then reverse each word in order. * eg.: in search of algorithmic elegance--> ecnagele cimhtiraglafo hcraes ni * and then: elegance algorithmic of search in */public char[] revertSentence(char[] str){int start = 0, end = 0, len;len = str.length;//reverse the whole string, will get: .yrt on si ereht ,ton od ro oDreverseStr(str, start, len-1);//get each word, and reverse itwhile(end < len){ if(str[end] != ' '){//get the new start for the next word in the string start = end; while(end < len && str[end] != ' ')end++;//back up to the end of the wordend--;reverseStr(str, start, end);} end++; //skip the empty space}return str;}private void reverseStr(char[] str, int start, int end){char temp;while(start < end){temp = str[start];str[start] = str[end];str[end] = temp;++start;--end;}}/* * convert a string to an int */public int strToInt(String str){int num = 0, len = str.length();boolean isNegative = false;int start = 0; if(str.charAt(0)== '-'){isNegative = true;start = 1;}for(int i = start; i < len; ++i){int temp = str.charAt(i);num *= 10;   //two key steps: Horner rulesnum += (temp-'0');} if(isNegative)num *= (-1);return num;}/* * convert an int to a string */public static final int MAX_DIGITS = 10;public String intToStr(int num){StringBuffer sb = new StringBuffer();boolean isNegative = false;char[] temp = new char[MAX_DIGITS + 1]; int i = 0;if(num < 0){isNegative = true;num *= -1;}do{temp[i++] = (char)((num % 10) + '0'); num /= 10; }while( num != 0);if(isNegative)sb.append('-');while( i > 0)sb.append(temp[--i]);  //good! return sb.toString();}}