C + + standard library type Bitset and its application

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The Bitset object is stored with each bit bit 0 or 1, which can be used to mark the presence or absence, the location subscript and the stored content to form a key-value pair. The advantage of using bit notation is that memory space can be saved, especially for mass data processing.

For example, the following questions: (1) A file is known to contain some telephone numbers, each number is 8 digits, the number of different numbers are counted, (2) 250 million integers to find out the number of distinct integers, memory space is not enough to accommodate the 250 million integers; (3) Someone has 8 stamps 5, 1 Stamps 4 , 1.8 Yuan of the Stamps 6, how many different kinds of postage can be obtained with one or several of these stamps?

The common denominator of the above 3 questions boils down to finding the number of non-duplicates in a pile of numbers- to repeat the problem . For the problem (3), in the 6*5*7 integer to repeat, we can use a char array or an array of int access, memory savings is not so obvious, but for (1) and (2), it is necessary to adopt the Bieset class library. (1) Medium: 8 bits maximum is 99 999 999, if each bit indicates whether a number exists, if each number on average 1 times, theoretically only need 100M bit (12.5MB) of memory.

1#include <iostream>2#include <bitset>//Bitset Class Library declaration3 using namespacestd; 4   5 intMain ()6 {  7     ConstUnsignedintA =189;//maximum postage 188 pt8Bitset<a> Bitvec;//Generating Bitset Objects9   Ten     intx =0, y =0, z =0;  One      for(x =0; X <=5; ++x) {   A          for(y =0; Y <=4; ++y) {   -              for(z =0; Z <=6; ++z) {   -bitvec[8* x +Ten* y + -* Z] =1;  the             }   -         }   -     }   -    +     intCount =0;  -      for(x =0; x<a; ++x) +     if(Bitvec[x]) Acount++;  atcout <<"Total:"<<Count -<<"types of postage combinations"<<Endl;  -    -     return 0;  -}

Reference Links:

http://blog.csdn.net/yushuai007008/article/details/7466945

http://dongxicheng.org/structure/bitmap/

http://www.cplusplus.com/reference/bitset/bitset/

C + + standard library type Bitset and its application