???????rand()
??????????:   rand
??????   ??:   ???????????
??????   ??:   int rand(void);
????????????: stdlib.h
??????????? :
????· rand()???????????????????????????????????????????????????????????????Χ??????????????
????· rand()??????????????Χ??0??RAND_MAX ??RAND_MAX???Χ??????32767???(int)???? unsigned int ??????65535?????????4294967295????????Χ??0~RAND_MAX??????????е????????????
????· ???δ?趨????????????????????????????1??
????· rand()????????α??????????????????????;?????????ú???srand()?????????
???????????:
#include <iostream>
using namespace std;
#include   <stdlib.h>
#include   <time.h>
#define MIN 1    //????????????Χ
#define MAX 10
int main()
{
int i;
srand((unsigned)time(0));
cout<<"Ten random numbers from "<<MIN<<
" to "<<MAX<<" :/n"<<endl;
for(i=0; i<10; i++)          //?????????
{
cout<<MIN + (int)MAX * rand() / (RAND_MAX + 1)<<"/t";
}
cout<<endl;
return   0;
}
????????srand()
??????????:   srand
??????   ??:   ????????????????
??????   ??:   void srand(unsigned  int  seed);
?????????????? stdlib.h
?????????????
????srand()????????rand()??????????????????????
????????seed????????????????????????time(0)????????NULL??????seed??
??????????seed??????????rand()????????????????λ??????
???????????:
#include <iostream>
using namespace std;
#include   <stdlib.h>
#include   <time.h>
#define MIN 0    //????????????Χ
#define MAX 99
int main()
{
int i;
srand((unsigned)time(NULL));
cout<<"Ten random numbers from "<<MIN<<
" to "<<MAX<<" :/n"<<endl;
for(i=0; i<10; i++)          //?????????
{
cout<<MIN + rand() % (MAX + MIN - 1)<<"/t";
}
cout<<endl;
return   0;
}
????????rand()??srand()????
????rand()??srand()????????????srand()???????????????????rand()???????????????
?????????????????????????1?????????????????????????????????????????????????壬????????ε?????????????????ú???srand()???????????????srand()?????????time???????????????????????ε???rand()?????????????????????????????????????
????????????????Χ???????????????
????????[a??b)??????????????(rand() % (b-a))+ a ????????a????b????
????????[a??b]??????????????(rand() % (b-a+1))+ a ????????a??b????
????????(a??b]??????????????(rand() % (b-a))+ a + 1 ??????????a??b????
????????????????ù????a + rand() % n ?????е?a????????n?????????Χ??
????????a??b??????????????????????a + (int)b * rand() / (RAND_MAX + 1)??
????????0??1??????????????????rand() / double(RAND_MAX)??
?????塢???????????????????
??????????????????????α?????????????СM??????????????????в??????С???ж??????????????????????????? СM????????е???????65535???????????????????????????????????????65535?????????65535???????????????????????????
???????????rand()??????????????????????????????????????????????????????α??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
?????????????
????#include <iostream>
????using namespace std;
????#include <stdlib.h>
????#include <time.h>
????int main()
????{
????int i;
????for (i=0; i<10; i++)      //????10???????
????{
????cout<<rand()<<"/t";
????}
????cout<<endl;
????return 0;
????}
??????????е?????????????У?
????41 18467 6334 26500 19169 15724 11478
????41 18467 6334 26500 19169 15724 11478 29358 26962 24464
?????????????????????У???????????????????????????????????????????????srand(time(NULL))?????srand()???????????????????????????????棬???????????????????????????
?????????????
????#include <iostream>
????using namespace std;
????#include <stdlib.h>
????#include <time.h>
????int main()
????{
????int i;
????srand((unsigned)time(NULL)); //??????????????
????for (i=0; i<10; i++)         //????10???????
????{
????cout<<rand()<<"/t";
????}
????cout<<endl;
????return 0;
????}
??????????е?????????????У?
????1294 18562 14141 18165 11910 29784 11070 13225 131 24405
????1774 25714 18734 16528 20825 17189 9848 8899 2503 5375