C语言第七周作业（函数，随机数）

1.

#include <stdio.h> int rather(int,int); int main(){ int m,n,min; printf("enter two numbers:"); scanf("%d %d",&m,&n); min = rather(n,m-n); long long int fact=1,facc=1; for(int i=1;i<=min;i++){ fact *=i; facc *=(m-i+1); } printf("%d",facc/fact); return 0; } int rather(int a,int b){ int flag; if (b<=a){ flag=b; }else{ flag=a; } return flag; }

第一次，按老师要求，化简公式，取long long int 型，可以使m达到15.

#include <stdio.h> double factorial(int); int main(){ double m,n; double result; printf("enter two numbers:"); scanf("%lf %lf",&m,&n); result = factorial(m)*1.0/(factorial(n)*factorial(m-n)); printf("%.lf",result); return 0; } double factorial(int k){ double fact=1; for(int i=1;i<=k;i++){ fact *=i; } return fact; }

第二次，直接把变量定义为double，可以算到m=170次方，算是极大地提升。

如果把第一种公式的化简应用到第二种里面，应该范围可以更大。

#include <stdio.h> double rather(double,double); int main(){ long double m,n,min; printf("enter two numbers:"); scanf("%lf %lf",&m,&n); min = rather(n,m-n); double fact=1,facc=1; for(int i=1;i<=min;i++){ fact *=i; facc *=(m-i+1); } printf("%.lf",facc/fact); return 0; } double rather(double a,double b){ int flag; if (b<=a){ flag=b; }else{ flag=a; } return flag; }

既化简了公式，又取变量为double类型，可以计算达到m=266，n=133，位数达到79位。

2.

（2）

#include <stdio.h> int check(int,int,int); int main(){ int x,y,n; printf("please enter three numbers:"); scanf("%d %d %d",&x,&y,&n); printf("%d",check(x,y,n)); return 0; } int check(int x,int y,int n){ int flag=0; if ((x>=0&&x<n)&&(y>=0&&y<n)){ flag=1; } return flag; }

（5）

#include <stdio.h> int num_digits(int); int main(){ int num; printf("please enter a number:"); scanf("%d",&num); printf("the number has %d digits.",num_digits(num)); return 0; } int num_digits(int x){ int cnt=0; while (x>0){ x /=10; cnt++; } return cnt; }

（6）

#include <stdio.h> int digit(int, int); int main(){ int n,k; printf("enter two numbers:"); scanf("%d %d",&n,&k); printf("第%d位数字是%d",k,digit(n,k)); return 0; } int digit(int n,int k){ int cnt=1; int flag=0; while (n>0){ if(cnt==k){ flag= n%10; break; } n /=10; cnt++; } return flag; }

3.

（5）

#include <stdio.h> #include <ctype.h> #include <string.h> int pinzi(char[]); int main(){ int i,j; char word[50]; printf("Enter a word:"); scanf("%s",&word); //printf("%s",word); printf("Scrabble value:%d",pinzi(word)); return 0; } int pinzi(char word[50]){ int i,len,value=0; len = strlen(word); for(i=0;i<len;i++){ char ch=toupper(word[i]); if (ch=='A'||ch=='E'||ch=='I'||ch=='L'||ch=='N'||ch=='O'||ch=='R'||ch=='S'||ch=='T'||ch=='U') value++; else if(ch=='D'||ch=='G') value +=2; else if(ch=='B'||ch=='C'||ch=='M'||ch=='P') value +=3; else if(ch=='F'||ch=='H'||ch=='V'||ch=='W'||ch=='Y') value +=4; else if(ch=='K') value +=5; else if(ch=='J'||ch=='X') value +=8; else if(ch=='Q'||ch=='Z') value +=10; //printf("%d\n",value); } return value; }

（14）

#include <stdio.h> #include <math.h> double square(double); int main(){ double x; printf("Enter a positive number:"); scanf("%lf",&x); printf("%lf",square(x)); return 0; } double square(double x){ double y=1; double m,t; do{ m=y; t=x/y; y =(y+x/y)/2; }while(fabs(m-y)>=10e-5 *y); return y; }

4.

（2）

#include <stdio.h> #include <math.h> double dist(double,double); double angel(double,double); int main(){ double x,y; printf("please enter two numbers:"); scanf("%lf %lf",&x,&y); //r=dist(x,y); //q=angel(x,y); printf("the distance is %.2lf\n",dist(x,y)); printf("the angel is %.2lf\n",angel(x,y)); return 0; } double dist(double x,double y){ return sqrt(x*x+y*y); } double angel(double x,double y){ return atan(y/x); }

5.

（5）

#include <stdio.h> #include <stdlib.h> #include <time.h> #include <windows.h> int flip(int);/* flip函数原型*/ void percentages(int,int); /* percentage 函数原型*/ int main(){ int heads; int numTosses = 1000; double sumperheads=0,sumpertails=0; srand(time(NULL)); for(int i=0;i<20;i++){ heads = flip(numTosses); percentages(numTosses,heads); sumperheads +=(float)heads/numTosses*100.0; sumpertails +=(float)(numTosses-heads)/numTosses*100.0; } printf("\n\nsumHeads came up %6.2f percent of the time.\n",sumperheads/20.0); printf("sumTails came up %6.2f percent of the time.\n",sumpertails/20.0); return 0; //这个方法抛掷硬币numTimes 次 //并且返回人头面的次数 } int flip(int numTimes){ int randValue; int heads=0; int i; for(i=1;i<=numTimes;i++){ randValue =1+rand()%100; if (randValue >50) heads++; } return heads; } //这个方法计算和 //人头面和反面辫子面的百分比 void percentages(int numTosses,int heads){ int tails; float perheads; if(numTosses ==0){ printf("There were no tosses, so no percentages can be calculated.\n"); }else { tails =numTosses-heads; printf("Number of coin tosses:%d\n",numTosses); printf(" Heads:%d Tails:%d\n",heads,tails); perheads=(float)heads/numTosses*100.0; //pertails=(float)(numTosses -heads)/numTosses* 100.0; printf("Heads came up %6.2f percent of the time.\n",perheads); printf("Tails came up %6.2f percent of the time.\n",100-perheads); } }

（6）

（a）

#include <stdio.h> #include <time.h> #include <stdlib.h> int main(){ int seed,number; srand(time(NULL)); seed=1+rand()%100; printf("the seed is %d\n",seed); int cnt=7; while (cnt>0){ printf("enter a number:"); scanf("%d",&number); cnt--; if (number==seed){ printf("Hooray,you have won!"); break; }else { if (number>seed){ printf("Wrong Number,Try Again\n"); printf("the number is too big!,you has %d chances\n",cnt); }else{ printf("Wrong Number,Try Again\n"); printf("the number is too small!,you have %d chances\n",cnt); } } } if (cnt==0){ printf("Sorry,you lose\n"); printf("the correct number is %d\n",seed); } return 0; }

(b)

#include <stdio.h> #include <time.h> #include <stdlib.h> void game(void); int main(){ game(); char choice; while (1) { rewind(stdin); printf("enter a letter:"); scanf("%c",&choice); if (choice=='y'||choice=='Y'){ game(); } else{ break; } } return 0; } void game(){ int seed,number; srand(time(NULL)); seed=1+rand()%100; printf("the seed is %d\n",seed); int cnt=7; while (cnt>0){ printf("enter a number:"); scanf("%d",&number); cnt--; if (number==seed){ printf("Hooray,you have won!"); break; }else { if (number>seed){ printf("Wrong Number,Try Again\n"); printf("the number is too big!,you has %d chances\n",cnt); }else{ printf("Wrong Number,Try Again\n"); printf("the number is too small!,you have %d chances\n",cnt); } } } if (cnt==0){ printf("Sorry,you lose\n"); printf("the correct number is %d\n",seed); } printf("Would you like to play again(y/n)?\n"); }

第二次用函数来实现，需要注意的细节还是比较多的。

（7）

#include <stdio.h> #include <time.h> #include <stdlib.h> void shuzu(int,int count[10]); int main(){ int i=0,j=0; int count[10]={0}; shuzu(i,count); while(j<10){ printf("the %d is %d percent.\n",j+1,count[j]); j++; } return 0; } void shuzu(int i,int count[]){ int seed; srand(time(NULL)); while(i<100){ seed=1+rand()%10; count[seed-1]++; i++; } }

当函数需要数组作为参数的时候，在这道题里面写成int count[]是对的，写成int count[10]也是对的，写成int *count也是对的。

但是写成int count确实错的。

（8）

#include <stdio.h> #include <time.h> #include <stdlib.h> int game1(int,int,int); int game2(int,int,int); int game3(int,int,int); int main(){ int shai1,shai2; int game; int money=50; srand(time(NULL)); while (money>0){ printf("please select a game:"); scanf("%d",&game); printf("please roll two dice\n"); shai1=1+rand()%6; shai2=1+rand()%6; switch (game){ case 1: money = game1(shai1,shai2,money); break; case 2: money = game2(shai1,shai2,money); break; case 3: money = game3(shai1,shai2,money); break; } } return 0; } int game1(int shai1,int shai2,int money){ if ((shai1+shai2==7)||(shai1+shai2==11)){ printf("the shai1=%d,the shai2=%d\n",shai1,shai2); printf("you won!\n"); }else{ money-=(shai1+shai2); printf("the shai1=%d,the shai2=%d\n",shai1,shai2); printf("you lose,the money has %d.\n",money); } return money; } int game2(int shai1,int shai2,int money){ if ((shai1+shai2)%2==0){ printf("the shai1=%d,the shai2=%d\n",shai1,shai2); printf("you won!\n"); }else{ money-=(shai1*shai2); printf("the shai1=%d,the shai2=%d\n",shai1,shai2); printf("you lose,the money has %d.\n",money); } return money; } int game3(int shai1,int shai2,int money){ if ((shai1>shai2) && (shai1>4)){ printf("the shai1=%d,the shai2=%d\n",shai1,shai2); printf("you won!\n"); }else{ money /=shai1; printf("the shai1=%d,the shai2=%d\n",shai1,shai2); printf("you lose,the money has %d.\n",money); } return money; }

6.

（12）

#include <stdio.h> #include <time.h> #include <stdlib.h> int main(){ char let0,let; int i; srand(time(NULL)); while(1){ let0=let; let='a'+rand()%26; i+=2; if ((let0=='a'&&let=='t')||(let0=='i'&&let=='s')||(let0=='h'&&let=='e')||(let0=='w'&&let=='e')||(let0=='u'&&let=='p')||(let0=='o'&&let=='n')){ break; } printf("all numbers have %d\n",let); } return 0; }

7.

（13）

#include <stdio.h> #include <time.h> #include <stdlib.h> int main(){ int i,j=0; srand(time(NULL)); for(i=500;i>0;i--){ int num,dist=0; while(1){ num=1+rand()%2; if(num>1){ dist+=2; }else{ dist-=1; } if (dist>=10){ j++; break; }else if (dist==0){ //printf("the dog will have a night."); break; } } } printf("the percent is %lf",j/500.0); }

8.

#include <stdlib.h> #include <stdio.h> #include <math.h> float gaussrand_NORMAL() { static float V1, V2, S; static int phase = 0; float X; if (phase == 0) { do { float U1 = (float) rand() / RAND_MAX; float U2 = (float) rand() / RAND_MAX; V1 = 2 * U1 - 1; V2 = 2 * U2 - 1; S = V1 * V1 + V2 * V2; } while (S >= 1 || S == 0); X = V1 * sqrt(-2 * log(S) / S); } else X = V2 * sqrt(-2 * log(S) / S); phase = 1 - phase; return X; } float gaussrand(float mean, float stdc) { return mean + gaussrand_NORMAL() * stdc; } int main() { float mean = 0; float stdc = 1; float data = 0; for(int i=0; i<100; ++i){ data = gaussrand(0, 1); printf("%f\t", data); } }

9.

随机数生成器程序

double randomExponential(double lambda) { double pv = 0.0; pv = (double)(rand()%100)/100; while(pv == 0) { pv = (double)(rand() % 100)/100; } pv = (-1 / lambda)*log(1-pv); return pv; }