[leetcode] Longest Substring Without Repeating Characters

/*
  * Use two points, pBeg and pEnd, pointing to the begin and end
  * of current substring without repeating respectively. Integer
  * Array pos[256] records the last occurrence position of each
  * ASCII character.
  *
  * For each loop, pEnd moved forward one character. If the new
  * character(i.e. str[pEnd], referred as newChar) has appeared
  * in current substring before, move pBeg to pos[newChar]+1,
  * and update pos[], len, etc.
  *
  * @author: HZT
  * @date: 2013-3-7
  *
  */
 
 #include <iostream>
 #include <memory>
 #include <cstring>
 using namespace std;
 
 int substring(string str){
     int strLen = str.length();
     if(strLen == 0) return 0;
     
     int maxLen = 1;
 
     int len = 1;
     int beg = 0, end = 0;
 
     int pos[256];
     memset(pos, -1, sizeof(pos));
     pos[str[0]-'\0'] = 0;
 
     while(true){
         end++;
         if(end >= strLen) break;
 
         int lastPos = pos[str[end]-'\0'];
         if(lastPos == -1){
             len++;
             lastPos = end;
             pos[str[end]-'\0'] = end;
         }
         else{
             len -= (lastPos - beg);
             for(int i=beg; i<=lastPos; i++){
                 if(pos[str[i]-'\0'] == i)
                     pos[str[i]-'\0'] = -1;
             }
             pos[str[end]-'\0'] = end;
             beg = lastPos + 1;
         }
 
         if(len > maxLen){
             maxLen = len;
         }
     }
 
     return maxLen;
 }
 
 
 int main(){
     string str = "bbbbb";
 
     cout << substring(str) << endl;
 
     return 0;
 }