diff --git a/source/_posts/answer6.md b/source/_posts/answer6.md new file mode 100644 index 0000000..8d0d546 --- /dev/null +++ b/source/_posts/answer6.md @@ -0,0 +1,267 @@ +--- +title: 第六次作业（答案） +date: 2020-11-20 17:40:16 +tags: +--- + +# 冒泡排序 + +```C +#include +#include +#include + +#define LEN 10 + +void swap(int a[], int i, int j) +{ + int tmp = a[i]; + a[i] = a[j]; + a[j] = tmp; +} + +void bubble_sort(int a[], int n) +{ + int done = 0; + for (int i = 0; i < n - 1; ++i) { + if (done) + return; + done = 1; + for (int j = 0; j < n - 1 - i; ++j) { + if (a[j] > a[j + 1]) { + swap(a, j, j + 1); + done = 0; + } + } + } +} + +void rand_array(int a[], int n) +{ + for (int i = 0; i < n; ++i) { + int tmp = rand() % 20 + 1; + a[i] = tmp; + } +} + +void print_array(int a[], int n) +{ + for (int i = 0; i < n; ++i) { + printf("%d ", a[i]); + } + printf("\n"); +} + +int main() +{ + srand(time(0)); + int a[LEN]; + printf("使用随机数填充数组：\n"); + rand_array(a, LEN); + print_array(a, LEN); + bubble_sort(a, LEN); + printf("排序过后的数组：\n"); + print_array(a, LEN); + return 0; +} +``` + +# 矩阵乘法 + +```C +#include + +void input_matrix(double mat[][100], int *row, int *column) +{ + printf("行："); + scanf("%d", row); + printf("列："); + scanf("%d", column); + printf("数据：\n"); + for (int i = 0; i < *row; ++i) { + for (int j = 0; j < *column; ++j) { + scanf("%lf", &mat[i][j]); + } + } +} + +void print_matrix(double mat[][100], int row, int column) +{ + for (int i = 0; i < row; ++i) { + for (int j = 0; j < column; ++j) { + printf("%f ", mat[i][j]); + } + printf("\n"); + } +} + +void matrix_mul(double mat_a[][100], double mat_b[][100], double mat_c[][100], + int a_row, int a_column, int b_column) +{ + for (int i = 0; i < a_row; ++i) { + for (int j = 0; j < b_column; ++j) { + mat_c[i][j] = 0; + for (int k = 0; k < a_column; ++k) { + mat_c[i][j] += mat_a[i][k] * mat_b[k][j]; + } + } + } +} + +int main() +{ + double mat_a[100][100]; + double mat_b[100][100]; + double mat_c[100][100]; + int a_row; + int a_column; + int b_row; + int b_column; + printf("请输入矩阵A：\n"); + input_matrix(mat_a, &a_row, &a_column); + printf("请输入矩阵B：\n"); + input_matrix(mat_b, &b_row, &b_column); + if (a_column != b_row) { + printf("A和B无法相乘！\n"); + return 0; + } + matrix_mul(mat_a, mat_b, mat_c, a_row, a_column, b_column); + print_matrix(mat_c, a_row, b_column); + return 0; +} +``` + +# P166 T13 + +```C +#include +#include + +void mystrcat(char a[], char b[]) +{ + int i = strlen(a) - 1; + for (int j = 0; b[j] != '\n'; ++i, ++j) { + a[i] = b[j]; + } + a[i] = '\0'; +} + +int main() +{ + printf("请输入第一个字符串，回车结束：\n"); + char a[200]; + fgets(a, 200, stdin); + printf("请输入第二个字符串，回车结束：\n"); + char b[100]; + fgets(b, 100, stdin); + mystrcat(a, b); + printf("连接之后的字符串是\n%s\n", a); + return 0; +} +``` + +# P216 T13 + +```C +#include + +double P(int n, double x) +{ + if (n == 0) { + return 1; + } else if (n == 1) { + return x; + } else { + return ((2 * n - 1) * x - P(n - 1, x) - (n - 1) * P(n - 2, x)) / n; + } +} + +int main() +{ + printf("请输入x: "); + double x; + scanf("%lf", &x); + printf("请输入n: "); + int n; + scanf("%d", &n); + printf("P_n(x) = %lf\n", P(n, x)); + return 0; +} +``` + +# P216 T14 + +```C +#include + +double score[5][3]; + +void Average_Student(void) +{ + for (int i = 0; i < 5; ++i) { + double avg = 0; + for (int j = 0; j < 3; ++j) { + avg += score[i][j]; + } + avg /= 3; + printf("第%d个学生的平均成绩是%f\n", i + 1, avg); + } +} + +void Average_Lesson(void) +{ + for (int i = 0; i < 3; ++i) { + double avg = 0; + for (int j = 0; j < 5; ++j) { + avg += score[j][i]; + } + avg /= 5; + printf("第%d门课程的平均成绩是%f\n", i + 1, avg); + } +} + +void Find_Max(void) +{ + double max = score[0][0]; + int max_i = 0, max_j = 0; + for (int i = 0; i < 5; ++i) { + for (int j = 0; j < 3; ++j) { + if (max < score[i][j]) { + max = score[i][j]; + max_i = i; + max_j = j; + } + } + } + printf("成绩最高的是第%d个学生的第%d门课程的成绩。\n", max_i + 1, max_j + 1); +} + +void Calc_Var(void) +{ + double sum_xi = 0; + double sum_xi2 = 0; + for (int i = 0; i < 3; ++i) { + for (int j = 0; j < 5; ++j) { + sum_xi2 += score[i][j]; + sum_xi2 += score[i][j] * score[i][j]; + } + } + double sigma = sum_xi2 / 15 - sum_xi * sum_xi / 225; + printf("方差是%f\n", sigma); +} + +int main() +{ + for (int i = 0; i < 5; ++i) { + for (int j = 0; j < 3; ++j) { + printf("请输入第%d个学生的第%d门成绩：", i + 1, j + 1); + scanf("%lf", &score[i][j]); + } + } + Average_Student(); + Average_Lesson(); + Find_Max(); + Calc_Var(); + return 0; +} +``` diff --git a/source/_posts/homework.md b/source/_posts/homework.md index ed398fa..f71d768 100644 --- a/source/_posts/homework.md +++ b/source/_posts/homework.md @@ -6,39 +6,45 @@ date: 2020-10-30 09:39:53 tags: --- +# 第六次作业 + +- [题目](/~zhaozuohong/homework6/) +- [答案](/~zhaozuohong/answer6/) +- [讲解](/~zhaozuohong/resources/Experiment6.pdf) + # 第一次大作业 -* [题目](/~zhaozuohong/big-homework1/) -* [答案](/~zhaozuohong/big-answer1/) -* [实验报告模板（ $\rm \LaTeX$ )](/~zhaozuohong/template1/) +- [题目](/~zhaozuohong/big-homework1/) +- [答案](/~zhaozuohong/big-answer1/) +- [实验报告模板（ $\rm \LaTeX$ )](/~zhaozuohong/template1/) # 第五次作业 -* [题目](/~zhaozuohong/homework5/) -* [答案](/~zhaozuohong/answer5/) -* [讲解](/~zhaozuohong/resources/Experiment5.pdf) +- [题目](/~zhaozuohong/homework5/) +- [答案](/~zhaozuohong/answer5/) +- [讲解](/~zhaozuohong/resources/Experiment5.pdf) # 第四次作业 -* [题目](/~zhaozuohong/homework4/) -* [答案](/~zhaozuohong/answer4/) -* [讲解](/~zhaozuohong/resources/Experiment4.pdf) +- [题目](/~zhaozuohong/homework4/) +- [答案](/~zhaozuohong/answer4/) +- [讲解](/~zhaozuohong/resources/Experiment4.pdf) # 第三次作业 -* [题目](/~zhaozuohong/homework3/) -* [答案](/~zhaozuohong/answer3) -* [测试数据](/~zhaozuohong/test3) -* [讲解](/~zhaozuohong/resources/Experiment3.pdf) +- [题目](/~zhaozuohong/homework3/) +- [答案](/~zhaozuohong/answer3) +- [测试数据](/~zhaozuohong/test3) +- [讲解](/~zhaozuohong/resources/Experiment3.pdf) # 第二次作业 -* [题目](/~zhaozuohong/homework2/) -* [答案](/~zhaozuohong/answer2) -* [讲解](/~zhaozuohong/resources/Experiment2.pptx) +- [题目](/~zhaozuohong/homework2/) +- [答案](/~zhaozuohong/answer2) +- [讲解](/~zhaozuohong/resources/Experiment2.pptx) # 第一次作业 -* [题目](/~zhaozuohong/homework1/) -* [答案](/~zhaozuohong/answer1) -* [讲解](/~zhaozuohong/resources/Experiment1.pptx) +- [题目](/~zhaozuohong/homework1/) +- [答案](/~zhaozuohong/answer1) +- [讲解](/~zhaozuohong/resources/Experiment1.pptx) diff --git a/source/_posts/homework6.md b/source/_posts/homework6.md new file mode 100644 index 0000000..c8cfec2 --- /dev/null +++ b/source/_posts/homework6.md @@ -0,0 +1,49 @@ +--- +title: 第六次作业（题目） +date: 2020-11-20 12:26:17 +tags: +mathjax: true +--- + +# 冒泡排序 + +对 10 个伪随机数冒泡排序，伪随机数产生方法可参考上面习题指导第 127 页，注意冒泡排序排好了要能提前退出。 + +# 矩阵乘法 + +实现两个矩阵相乘。 + +# P166 T13 + +编一程序，将两个字符串连接起来，不要用`strcat`函数。 + +# P216 T13 + +用递归方法求 $n$ 阶勒让德多项式的值，递归公式为： + +$$ +\begin{equation*} + P_{n}(x) = \left \{ + \begin{array}{ll} + 1 & (n = 0) \\ + x & (n = 1) \\ + ((2n-1) \times x P_{n-1}(x) - (n-1) \times P_{n-2}(x) ) / n & (n \geq 1) + \end{array} + \right . +\end{equation*} +$$ + +# P216 T14 + +输入 5 个学生 3 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. 每门课的平均分； +3. 找出所有 15 个中最高的所对应的学生和课程； +4. 计算平均分方差。 + +$$ +\begin{equation*} +\sigma = \frac{1}{n} \sum x_i^2 - \left ( \frac{\sum x_i}{n} \right ) ^2 +\end{equation*} +$$