C 随机数，获取min至max之间的随机数（尽可能公平）
#include <unistd.h>#include <stdlib.h>#include <time.h>#include <math.h>#include <stdio.h>static int getRand(int min, int max);int count=20;int main(int argc, char **argv){int i;int rd;int h_ct=0; int min_ct1 = 0;int z_ct=0; int max_ct1 = 0; int max_ct = 0; int min=atoi(argv[1]); int max=atoi(argv[2]); int min1=min+1; int max1=max-1; if(argc>3) count = atoi(argv[3]); printf("min=%d, max=%d\n", min, max);for(i=0;i<count;i++){rd = getRand(min,max);if(rd==max) h_ct++;else if(rd==min) z_ct++;else if(rd==min1) min_ct1++;else if(rd==max1) max_ct1++;else if(rd>max) max_ct++;}printf("Times of : min=%d, min+1=%d, max-1=%d, max=%d, big than max=%d\n",z_ct, min_ct1, max_ct1, h_ct, max_ct);return 0;}static int srand_seed_set = 0; //#define RD_PIECE 1/RAND_MAX;static int getRand(int min, int max){if(!srand_seed_set){srand_seed_set = 1;time_t t;srand((unsigned) time(&t));} if(max < min) return min; double m = 1.0/(max-min+1);double d = ((double)rand())/RAND_MAX;return min+d/m;}
效果：
[zty@lein ~]$ gcc -o t1 t1.c -lm && ./t1 21 112 2000000min=21, max=112Times of : min=22005, min+1=21698, max-1=21651, max=21758, big than max=0[zty@lein ~]$ ./t1 1 100 20000000 min=1, max=100Times of : min=200198, min+1=199927, max-1=200231, max=200204, big than max=0[zty@lein ~]$ ./t1 11 133 20000000 min=11, max=133Times of : min=162382, min+1=162602, max-1=162525, max=162750, big than max=0