C程序设计(第5版)谭浩强习题解答
第7章 用函数实现模块化程序设计
1.写两个函数,分别求两个整数的最大公约数和最小公倍数,用主函数调用这两个函数,并输出结果。两个整数由键盘输人。
//7.1.1
#include <stdio.h>
int main()
{int hcf(int, int);int lcd(int, int, int);int u, v, h, l;scanf("%d,%d", &u, &v);h = hcf(u, v);printf("H.C.F=%d\n", h);l = lcd(u, v, h);printf("L.C.D=%d\n", l);return 0;
}int hcf(int u, int v)
{int t, r;if (v > u){t = u; u = v; v = t;}while ((r = u % v) != 0){u = v;v = r;}return(v);
}int lcd(int u, int v, int h)
{return(u*v / h);
}//7.1.2
#include <stdio.h>
int Hcf, Lcd;
int main()
{void hcf(int, int);void lcd(int, int);int u, v;scanf("%d,%d", &u, &v);hcf(u, v);lcd(u, v);printf("H.C.F=%d\n", Hcf);printf("L.C.D=%d\n", Lcd);return 0;
}void hcf(int u, int v)
{int t, r;if (v > u){t = u; u = v; v = t;}while ((r = u % v) != 0){u = v;v = r;}Hcf = v;
}void lcd(int u, int v)
{Lcd = u * v / Hcf;
}
2.求方程 ax2+bx+c=0的根,用3个函数分别求当:b 2−4ac大于0、等于0和小于0时的根并输出结果。从主函数输入a,b,c的值。
#include <stdio.h>
#include <math.h>
float x1, x2, disc, p, q;
int main()
{void greater_than_zero(float, float);void equal_to_zero(float, float);void smaller_than_zero(float, float);float a, b, c;printf("input a,b,c:");scanf("%f,%f,%f", &a, &b, &c);printf("equation: %5.2f*x*x+%5.2f*x+%5.2f=0\n", a, b, c);disc = b * b - 4 * a*c;printf("root:\n");if (disc > 0){greater_than_zero(a, b);printf("x1=%f\t\tx2=%f\n", x1, x2);}else if (disc == 0){equal_to_zero(a, b);printf("x1=%f\t\tx2=%f\n", x1, x2);}else{smaller_than_zero(a, b);printf("x1=%f+%fi\tx2=%f-%fi\n", p, q, p, q);}return 0;
}void greater_than_zero(float a, float b)
{x1 = (-b + sqrt(disc)) / (2 * a);x2 = (-b - sqrt(disc)) / (2 * a);
}void equal_to_zero(float a, float b)
{x1 = x2 = (-b) / (2 * a);
}void smaller_than_zero(float a, float b)
{p = -b / (2 * a);q = sqrt(-disc) / (2 * a);
}
3.写一个判素数的函数,在主函数输人一个整数,输出是否为素数的信息。
#include <stdio.h>
int main()
{int prime(int);int n;printf("input an integer:");scanf("%d", &n);if (prime(n))printf("%d is a prime.\n", n);elseprintf("%d is not a prime.\n", n);return 0;
}int prime(int n)
{int flag = 1, i;for (i = 2; i < n / 2 && flag == 1; i++)if (n%i == 0)flag = 0;return(flag);
}
4.写一个函数,使给定的一个3X3的二维整型数组转置,即行列互换。
#include <stdio.h>
#define N 3
int array[N][N];
int main()
{void convert(int array[][3]);int i, j;printf("input array:\n");for (i = 0; i < N; i++)for (j = 0; j < N; j++)scanf("%d", &array[i][j]);printf("\noriginal array :\n");for (i = 0; i < N; i++){for (j = 0; j < N; j++)printf("%5d", array[i][j]);printf("\n");}convert(array);printf("convert array:\n");for (i = 0; i < N; i++){for (j = 0; j < N; j++)printf("%5d", array[i][j]);printf("\n");}return 0;
}void convert(int array[][3])
{int i, j, t;for (i = 0; i < N; i++)for (j = i + 1; j < N; j++){t = array[i][j];array[i][j] = array[j][i];array[j][i] = t;}
}
5.写一个函数,使输人的一个字符串按反序存放,在主函数中输入和输出字符串。
#include <stdio.h>
#include <string.h>
int main()
{void inverse(char str[]);char str[100];printf("input string:");scanf("%s", str);inverse(str);printf("inverse string:%s\n", str);return 0;
}void inverse(char str[])
{char t;int i, j;for (i = 0, j = strlen(str); i < (strlen(str) / 2); i++, j--){t = str[i];str[i] = str[j - 1];str[j - 1] = t;}
}
6.写一个函数,将两个字符串连接。
#include <stdio.h>
int main()
{void concatenate(char string1[], char string2[], char string[]);char s1[100], s2[100], s[100];printf("input string1:");scanf("%s", s1);printf("input string2:");scanf("%s", s2);concatenate(s1, s2, s);printf("\nThe new string is %s\n", s);return 0;
}void concatenate(char string1[], char string2[], char string[])
{int i, j;for (i = 0; string1[i] != '\0'; i++)string[i] = string1[i];for (j = 0; string2[j] != '\0'; j++)string[i + j] = string2[j];string[i + j] = '\0';
}
7.写一个函数,将一个字符串中的元音字母复制到另一字符串,然后输出。
#include <stdio.h>
int main()
{void cpy(char[], char[]);char str[80], c[80];printf("input string:");gets(str);cpy(str, c);printf("The vowel letters are:%s\n", c);return 0;
}void cpy(char s[], char c[])
{int i, j;for (i = 0, j = 0; s[i] != '\0'; i++)if (s[i] == 'a' || s[i] == 'A' || s[i] == 'e' || s[i] == 'E' || s[i] == 'i' ||s[i] == 'I' || s[i] == 'o' || s[i] == 'O' || s[i] == 'u' || s[i] == 'U'){c[j] = s[i];j++;}c[j] = '\0';
}
8.写一个函数,输人一个4位数字,要求输出这4个数字字符,但每两个数字间空一个空格。如输人1990,应输出“1 9 9 0”。
#include <stdio.h>
#include <string.h>
int main()
{char str[80];void insert(char[]);printf("input four digits:");scanf("%s", str);insert(str);return 0;
}void insert(char str[])
{int i;for (i = strlen(str); i > 0; i--){str[2 * i] = str[i];str[2 * i - 1] = ' ';}printf("output:\n%s\n", str);
}
9.编写一个函数,由实参传来一个字符串,统计此字符串中字母、数字、空格和其他字符的个数,在主函数中输人字符串以及输出上述的结果。
#include <stdio.h>
int letter, digit, space, others;
int main()
{void count(char[]);char text[80];printf("input string:\n");gets(text);printf("string:");puts(text);letter = 0;digit = 0;space = 0;others = 0;count(text);printf("\nletter:%d\ndigit:%d\nspace:%d\nothers:%d\n", letter, digit, space, others);return 0;
}void count(char str[])
{int i;for (i = 0; str[i] != '\0'; i++)if ((str[i] >= 'a'&& str[i] <= 'z') || (str[i] >= 'A' && str[i] <= 'Z'))letter++;else if (str[i] >= '0' && str[i] <= '9')digit++;else if (str[i] == 32)space++;elseothers++;
}
10.写一个函数,输人一行字符,将此字符串中最长的单词输出。
#include <stdio.h>
#include <string.h>
int main()
{int alphabetic(char);int longest(char[]);int i;char line[100];printf("input one line:\n");gets(line);printf("The longest word is :");for (i = longest(line); alphabetic(line[i]); i++)printf("%c", line[i]);printf("\n");return 0;
}int alphabetic(char c)
{if ((c >= 'a' && c <= 'z') || (c >= 'A'&&c <= 'z'))return(1);elsereturn(0);
}int longest(char string[])
{int len = 0, i, length = 0, flag = 1, place = 0, point;for (i = 0; i <= strlen(string); i++)if (alphabetic(string[i]))if (flag){point = i;flag = 0;}elselen++;else{flag = 1;if (len >= length){length = len;place = point;len = 0;}}return(place);
}
11.写一个函数,用“起泡法”对输人的10个字符按由小到大顺序排列。
#include <stdio.h>
#include <string.h>
#define N 10
char str[N];
int main()
{void sort(char[]);int i, flag;for (flag = 1; flag == 1;){printf("input string:\n");scanf("%s", &str);if (strlen(str) > N)printf("string too long,input again!");elseflag = 0;}sort(str);printf("string sorted:\n");for (i = 0; i < N; i++)printf("%c", str[i]);printf("\n");return 0;
}void sort(char str[])
{int i, j;char t;for (j = 1; j < N; j++)for (i = 0; (i < N - j) && (str[i] != '\0'); i++)if (str[i] > str[i + 1]){t = str[i];str[i] = str[i + 1];str[i + 1] = t;}
}
12.用牛顿迭代法求根。方程为ax3+bx 2+cx+d=0,系数a,b,c,d的值依次为1,2,3,4,由主函数输人。求x在1附近的一个实根。求出根后由主函数输出。
#include <stdio.h>
#include <math.h>
int main()
{float solut(float a, float b, float c, float d);float a, b, c, d;printf("input a,b,c,d:");scanf("%f,%f,%f,%f", &a, &b, &c, &d);printf("x=%10.7f\n", solut(a, b, c, d));return 0;
}float solut(float a, float b, float c, float d)
{float x = 1, x0, f, f1;do{x0 = x;f = ((a*x0 + b)*x0 + c)*x0 + d;f1 = (3 * a*x0 + 2 * b)*x0 + c;x = x0 - f / f1;} while (fabs(x - x0) >= 1e-3);return(x);
}
13.用递归方法求n阶勒让德多项式的值,递归公式为
#include <stdio.h>
#define N 10
#define M 5
float score[N][M];
float a_stu[N], a_cour[M];
int r, c;int main()
{int i, j;float h;float s_var(void);float highest();void input_stu(void);void aver_stu(void);void aver_cour(void);input_stu();aver_stu();aver_cour();printf("\n NO. cour1 cour2 cour3 cour4 cour5 aver\n");for (i = 0; i < N; i++){printf("\n NO %2d ", i + 1);for (j = 0; j < M; j++)printf("%8.2f", score[i][j]);printf("%8.2f\n", a_stu[i]);}printf("\naverage:");for (j = 0; j < M; j++)printf("%8.2f", a_cour[j]);printf("\n");h = highest();printf("highest:%7.2f NO. %2d course %2d\n", h, r, c);printf("variance %8.2f\n", s_var());return 0;
}void input_stu(void)
{int i, j;for (i = 0; i < N; i++){printf("\ninput score of student%2d:\n", i + 1);for (j = 0; j < M; j++)scanf("%f", &score[i][j]);}
}void aver_stu(void)
{int i, j;float s;for (i = 0; i < N; i++){for (j = 0, s = 0; j < M; j++)s += score[i][j];a_stu[i] = s / 5.0;}
}void aver_cour(void)
{int i, j;float s;for (j = 0; j < M; j++){s = 0;for (i = 0; i < N; i++)s += score[i][j];a_cour[j] = s / (float)N;}
}float highest()
{float high;int i, j;high = score[0][0];for (i = 0; i < N; i++)for (j = 0; j < M; j++)if (score[i][j] > high){high = score[i][j];r = i + 1;c = j + 1;}return(high);
}float s_var(void)
{int i;float sumx, sumxn;sumx = 0.0;sumxn = 0.0;for (i = 0; i < N; i++){sumx += a_stu[i] * a_stu[i];sumxn += a_stu[i];}return(sumx / N - (sumxn / N)*(sumxn / N));
}
14.输人10个学生5门课的成绩,分别用函数实现下列功能:
①计算每个学生的平均分;
②计算每门课的平均分;
③找出所有50个分数中最高的分数所对应的学生和课程;
④计算平均分方差:
其中,x;为某一学生的平均分。
#include <stdio.h>
#define N 10
#define M 5
float score[N][M];
float a_stu[N], a_cour[M];
int r, c;int main()
{int i, j;float h;float s_var(void);float highest();void input_stu(void);void aver_stu(void);void aver_cour(void);input_stu();aver_stu();aver_cour();printf("\n NO. cour1 cour2 cour3 cour4 cour5 aver\n");for (i = 0; i < N; i++){printf("\n NO %2d ", i + 1);for (j = 0; j < M; j++)printf("%8.2f", score[i][j]);printf("%8.2f\n", a_stu[i]);}printf("\naverage:");for (j = 0; j < M; j++)printf("%8.2f", a_cour[j]);printf("\n");h = highest();printf("highest:%7.2f NO. %2d course %2d\n", h, r, c);printf("variance %8.2f\n", s_var());return 0;
}void input_stu(void)
{int i, j;for (i = 0; i < N; i++){printf("\ninput score of student%2d:\n", i + 1);for (j = 0; j < M; j++)scanf("%f", &score[i][j]);}
}void aver_stu(void)
{int i, j;float s;for (i = 0; i < N; i++){for (j = 0, s = 0; j < M; j++)s += score[i][j];a_stu[i] = s / 5.0;}
}void aver_cour(void)
{int i, j;float s;for (j = 0; j < M; j++){s = 0;for (i = 0; i < N; i++)s += score[i][j];a_cour[j] = s / (float)N;}
}float highest()
{float high;int i, j;high = score[0][0];for (i = 0; i < N; i++)for (j = 0; j < M; j++)if (score[i][j] > high){high = score[i][j];r = i + 1;c = j + 1;}return(high);
}float s_var(void)
{int i;float sumx, sumxn;sumx = 0.0;sumxn = 0.0;for (i = 0; i < N; i++){sumx += a_stu[i] * a_stu[i];sumxn += a_stu[i];}return(sumx / N - (sumxn / N)*(sumxn / N));
}
15.写几个函数:
①输人10个职工的姓名和职工号;
②按职工号由小到大顺序排序,姓名顺序也随之调整;
③要求输人一个职工号,用折半查找法找出该职工的姓名,从主函数输人要查找的职工号,输出该职工姓名。
#include <stdio.h>
#include <string.h>
#define N 10
int main()
{void input(int[], char name[][8]);void sort(int[], char name[][8]);void search(int, int[], char name[][8]);int num[N], number, flag = 1, c;char name[N][8];input(num, name);sort(num, name);while (flag == 1){printf("\ninput number to look for:");scanf("%d", &number);search(number, num, name);printf("continue ot not(Y/N)?");getchar();c = getchar();if (c == 'N' || c == 'n')flag = 0;}return 0;
}void input(int num[], char name[N][8])
{int i;for (i = 0; i < N; i++){printf("input NO.: ");scanf("%d", &num[i]);printf("input name: ");getchar();gets(name[i]);}
}void sort(int num[], char name[N][8])
{int i, j, min, templ;char temp2[8];for (i = 0; i < N - 1; i++){min = i;for (j = i; j < N; j++)if (num[min] > num[j]) min = j;templ = num[i];strcpy(temp2, name[i]);num[i] = num[min];strcpy(name[i], name[min]);num[min] = templ;strcpy(name[min], temp2);}printf("\n result:\n");for (i = 0; i < N; i++)printf("\n %5d%10s", num[i], name[i]);
}void search(int n, int num[], char name[N][8])
{int top, bott, mid, loca, sign;top = 0;bott = N - 1;loca = 0;sign = 1;if ((n < num[0]) || (n > num[N - 1]))loca = -1;while ((sign == 1) && (top <= bott)){mid = (bott + top) / 2;if (n == num[mid]){loca = mid;printf("NO. %d , his name is %s.\n", n, name[loca]);sign = -1;}else if (n < num[mid])bott = mid - 1;elsetop = mid + 1;}if (sign == 1 || loca == -1)printf("%d not been found.\n", n);
}
16.写一个函数,输人一个十六进制数,输出相应的十进制数。
#include <stdio.h>
#define MAX 1000
int main()
{int htoi(char s[]);int c, i, flag, flag1;char t[MAX];i = 0;flag = 0;flag1 = 1;printf("input a HEX number:");while ((c = getchar()) != '\0' && i < MAX&& flag1){if (c >= '0' && c <= '9' || c >= 'a' && c <= 'f' || c >= 'A' && c <= 'F'){flag = 1;t[i++] = c;}else if (flag){t[i] = '\0';printf("decimal number %d\n", htoi(t));printf("continue or not?");c = getchar();if (c == 'N' || c == 'n')flag1 = 0;else{flag = 0;i = 0;printf("\ninput a HEX number:");}}}return 0;
}int htoi(char s[])
{int i, n;n = 0;for (i = 0; s[i] != '\0'; i++){if (s[i] >= '0'&& s[i] <= '9')n = n * 16 + s[i] - '0';if (s[i] >= 'a' && s[i] <= 'f')n = n * 16 + s[i] - 'a' + 10;if (s[i] >= 'A' && s[i] <= 'F')n = n * 16 + s[i] - 'A' + 10;}return(n);
}
17.用递归法将一个整数n转换成字符串。例如,输人483,应输出字符串”483”。n的位数不确定,可以是任意位数的整数。
#include <stdio.h>
int main()
{void convert(int n);int number;printf("input an integer: ");scanf("%d", &number);printf("output: ");if (number < 0){putchar('-'); putchar(' '); //先输出一个‘-’号和空格 number = -number;}convert(number);printf("\n");return 0;
}void convert(int n)
{int i;if ((i = n / 10) != 0)convert(i);putchar(n % 10 + '0');putchar(32);
}
18.给出年、月、日,计算该日是该年的第几天。
#include <stdio.h>
int main()
{int sum_day(int month, int day);int leap(int year);int year, month, day, days;printf("input date(year,month,day):");scanf("%d,%d,%d", &year, &month, &day);printf("%d/%d/%d ", year, month, day);days = sum_day(month, day); //调用函数sum_day if (leap(year) && month >= 3) //调用函数leap days = days + 1;printf("is the %dth day in this year.\n", days);return 0;
}int sum_day(int month, int day) //函数sum_day:计算日期
{int day_tab[13] = { 0,31,28,31,30,31,30,31,31,30,31,30,31 };int i;for (i = 1; i < month; i++)day += day_tab[i]; //累加所在月之前天数 return(day);
} //函数leap:判断是否为闰年 int leap(int year)
{int leap;leap = year % 4 == 0 && year % 100 != 0 || year % 400 == 0;return(leap);
}