"Prove safety offer" fifty-title II: the first character stream of characters appear only once

// interview questions 50 (2): The first character stream of characters appear only once
 // Title: Please implement a function to find the first character stream of characters appear only once. For example, when the
 // time character stream reads only the first two characters "go", the first character appears only once is 'g'. When the characters from the
 // time character stream reads the first six characters "google", it appears only once in the first character is 'l'. 

#include <cstdio> 
#include <Vector> 
#include <Limits>

using namespace std;

class CharStatistics
{
public:
    CharStatistics (): index ( 0 )   // index = 0 when initializing the hash table, a bit like a constructor 
    {
         for ( int I = 0 ; I < 256 ; ++ I)
            occurrence[i] = -1;
    }

    void the Insert ( char CH)   // insertion position of the current character into the hash table 
    {
         IF (occurrence [CH] == - . 1 )   // there have been no 
            occurrence [CH] = index;
         the else  IF (occurrence [CH]> = 0 )   // number of occurrences of 1 time or more 
            occurrence [CH] = - 2 ;

        ++index;
    }

    char FirstAppearingOnce()
    {
        char CH = ' \ 0 ' ;
         int minIndex the numeric_limits = < int ;> :: max ()   // maximum value of type int

        for (int i = 0; i < 256; ++i)
        {
            // occur once and the most forward position of the character 
            IF (occurrence [I]> = 0 && occurrence [I] < minIndex)
            {
                CH = ( char ) I;   // convert character 

                minIndex = occurrence [I];   // update the minimum position 
            }
        }
        return ch;
    }

private:
    // occurrence[i]: A character with ASCII value i;
    // occurrence[i] = -1: The character has not found;
    // occurrence[i] = -2: The character has been found for mutlple times
    // occurrence[i] >= 0: The character has been found only once
    int occurrence[256];  //hash表
    int index;  //当前字符流的位数
};

// ==================== test code ==================== 
void the Test ( const  char * TestName, CharStatistics chars, char expected)
{
    if (testName != nullptr)
        printf("%s begins: ", testName);

    if (chars.FirstAppearingOnce() == expected)
        printf("Passed.\n");
    else
        printf("FAILED.\n");
}

int main(int argc, char* argv[])
{
    CharStatistics chars;

    Test("Test1", chars, '\0');

    chars.Insert('g');
    Test("Test2", chars, 'g');

    chars.Insert('o');
    Test("Test3", chars, 'g');

    chars.Insert('o');
    Test("Test4", chars, 'g');

    chars.Insert('g');
    Test("Test5", chars, '\0');

    chars.Insert('l');
    Test("Test6", chars, 'l');

    chars.Insert('e');
    Test("Test7", chars, 'l');

    return 0;
}

Test code

Analysis: The hash table when you need multiple passes with a nice string.

class Solution
{
public:
    
    Solution() : index(0)
    {
        for (int i = 0; i < 256; ++i)
            occurrence[i] = -1;
    }
    
    //Insert one char from stringstream
    void Insert(char ch)
    {
         if (occurrence[ch] == -1)
             occurrence[ch] = index;
         else if (occurrence[ch] >= 0)
             occurrence[ch] = -2;
        
        ++index;
    }
    //return the first appearence once char in current stringstream
    char FirstAppearingOnce()
    {
        char ch = '#';
        int minIndex = numeric_limits<int>::max();
        
        for (int i = 0; i < 256; ++i)
        {
            if (occurrence[i] >= 0 && occurrence[i] < minIndex)
            {
                ch = (char)i;
                minIndex = occurrence[i];
            }
        }
        return ch;
    }
 private:
    int occurrence[256];
    int index;
    
};

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