C++의 큰 난수 에 관 한 문 제 를 간단히 이야기 하 다.

int littleRand(int min, int max) 
{ 
 //        RAND_MAX     0x7fff，     RAND_MAX*RAND_MAX，  int   
 
 if (min > max) 
 { 
 min = max; 
 } 
 
 int randV = rand() % (max - min + 1); 
 
 int randResult = min + randV; 
 return randResult; 
} 

int bigRand(int min, int max) 
{ 
 //        RAND_MAX     0x7fff，     RAND_MAX*RAND_MAX，  int   
 
 if (min > max) 
 { 
 min = max; 
 } 
 
 int rand1 = rand() % 10000; 
 int rand2 = rand() % 10000; 
 int randV = (rand1 * rand2) % (max - min + 1); 
 
 int randResult = min + randV; 
 return randResult; 
} 

int main() 
{ 
 srand(time(0)); 
 std::map<int, int> a; 
 std::map<int, int> b; 
 for (int i = 0; i < 1000000; i ++) 
 { 
 a[bigRand(1, 10)]++; 
 b[littleRand(1, 10)]++; 
 } 
 for (int i = 1; i <= 10; ++ i) 
 { 
 cout << i <<": \t"<< a[i] << " \t " << b[i] << endl; 
 } 
 
 return 0; 
} 

std::map<int, int> r; 
for(int i = 0; i < 10; ++i) 
{ 
 for (int j = 0; j < 10; ++j) { 
 r[i * j %10]++; 
 } 
} 
for (int i = 0 ; i < 10; ++i) { 
 cout << i <<"\t"<< r[i] << endl; 
} 

0 27
1 4
2 12
3 4
4 12
5 9
6 12
7 4
8 12
9 4

int bigRand(int min, int max) 
{ 
 if (min > max) 
 { 
 min = max; 
 } 
 
 int rand1 = rand() % 10000; 
 int rand2 = rand() % 10000; 
 int randV = (rand1 * 10000 + rand2) % (max - min + 1);//     
 
 int randResult = min + randV; 
 return randResult; 
} 

#include <stdio.h> 
#include <stdlib.h> 
#include <time.h> 
unsigned long ulrand(void) { 
 return ( 
 (((unsigned long)rand()<<24)&0xFF000000ul) 
 |(((unsigned long)rand()<<12)&0x00FFF000ul) 
 |(((unsigned long)rand() )&0x00000FFFul)); 
} 
int i; 
unsigned long ul; 
void main() { 
 srand(time(NULL)); 
 for (i=0;i<10;i++) { 
 ul=ulrand(); 
 printf("%010lu 0x%08x
",ul,ul); 
 } 
} 

int BigRand() 
{ 
 return RAND_MAX*rand() + rand(); 
}