C primer plus
第10章
第1题：
#include
#define MONTHS 12
#define YEARS 5
int main(void)
{
const float rain[YEARS][MONTHS]={
{4.3,4.3,4.3,3.0,2.0,1.2,0.2,0.2,0.4,2.4,3.5,6.6},
{8.5,8.2,1.2,1.6,2.4,0.0,5.2,0.9,0.3,0.9,1.4,7.3},
{9.1,8.5,6.7,4.3,2.1,0.8,0.2,0.2,1.1,2.3,6.1,8.4},
{7.2,9.9,8.4,3.3,1.2,0.8,0.4,0.0,0.6,1.7,4.3,6.2},
{7.6,5.6,3.8,2.8,3.8,0.2,0.0,0.0,0.0,1.3,2.6,5.2}
};
int year, month;
float subtot, total;
float(*pr)[MONTHS];
pr = rain;
printf("YEAR RAINFALL (inches)n");
for (year = 0, total = 0; year < YEARS; year++)
{
for (month = 0, subtot = 0; month < MONTHS; month++)
{
subtot += *(*(pr + year) + month); #注：（pr+year），其中year是数组的列，当year=1时，pr+0表示该数组的第一列, 所以*(pr+0)也就表示rain[0]它是一个地址，表示rain[0][0]的值的地址，也就是&rain[0][0]当让其+month的话就会列遍数组每个月对于的值的地址，之后再用一个解引用，可以表示每个月的值。二维数组的指针名可以记忆为rain[m][n]=*(*(rain+m)+n)
}
printf("%5d %15.1fn", 2010 + year, subtot);
total += subtot;
}
printf("nThe yearly average is %.1f inches.nn",total / YEARS);
printf("MONTHLY AVERAGES:nn");
printf("JAN FEB MAR APR MAY JUN JUL AUG SEP OCT");
printf("NOV DECn");
for (month = 0; month < MONTHS; month++)
{
for (year = 0, subtot = 0; year < YEARS; year++)
{
subtot += *(*(pr + year) + month);
}
printf("%4.1f", subtot / YEARS);
}
printf("n");
return 0;
}
第2题：
#include
void copy_arr(double x[], double source[], int n);#注：也可以把x[]定义成x*两者没有区别都表示地址。
void copy_ptr(double *y, double source[], int n);
void copy_ptrs(double *z, double source[], double *b);
int main(void)
{
double target1[5];
double target2[5];
double target3[5];
double source[5] = { 1.1,2.2,3.3,4.4,5.5 };
copy_arr(target1, source, 5); #注：函数中的前两个实参都相当于指针，也就地址。
copy_ptr(target2, source, 5);
copy_ptrs(target3, source, (source + 5));
}
void copy_arr(double x[], double source[], int n)
{
int i;
for (i = 0; i < n; i++) {
x[i] = source[i];
printf("%g ", x[i]);
}
}
void copy_ptr(double* y, double source[], int n)
{
int i;
putchar('n');
for (i = 0; i < n; i++)
{
*(y + i) = *(source + i);
printf("%g ", *(y + i));
}
}
void copy_ptrs(double* z, double source[], double* b)
{
int i;
putchar('n');
for (i = 0; i < b-source; i++) {
*(z + i) = *(source + i);
printf("%g ", *(z + i));
}
}
第3题：
#include
int get_max(int target[], int n);
int main (void){
int m;
int source[5] = { 1,2,3,3,3 };
int size = sizeof source / sizeof source[0]; #注：sizeof运算符给出它运算对象的大小，sizeof source是整个数组的大小也是4*5为20，source[0]是数组中一个元素的大小为4.
m=get_max(source, size);
printf("The max number of this list is %d", m);
return 0;
}
int get_max(int target[],int n) {
int i;
int max = target[0]; #注：一开始是尝试直接用sizeof target/sizeof target[0]表示数组长度的，但由于该函数中定义的target其实是一个指针，所以它的sizeof 大小是8字节，而target[0]是一个整数值，是4字节，结果就是2，所以定义数组的长度需要用到数组的名字。所以需要在主函数中计算数组长度。
for (i = 0; i < n; i++) {
if (max < target[i]) {
max = target[i];
}
}
return max;
}
第4题：
#include
int get_max(double target[], int n);
int main(void) {
int m;
double source[] = { 2.3,5.6,7.8,9.0,11.2,15.5,10.1,11.2,13.3 };
int size = sizeof source / sizeof source[0];
m = get_max(source, size);
printf("The max number is %g, and it is the %dth of the list",source[m], m);
return 0;
}
int get_max(double target[], int n) {
int i;
int mark;
double max = target[0];
for (i = 0; i < n; i++) {
if (max < target[i] ) {
max = target[i];
mark = i;
}
}
return mark;
}
第5题：
#include
double get_diff(double target[], int n);
int main(void) {
double d;
double source[] = { 2.3,5.6,7.8,9.0,11.2,15.5,10.1,11.2,13.3 };
int size = sizeof source / sizeof source[0];
d = get_diff(source, size);
printf("The max number - min number in the list is %g", d);
return 0;
}
double get_diff(double target[], int n) {
int i, j;
double max, min, diff;
max = target[0];
min = target[0];
for (i = 0; i < n; i++) {
if (max < target[i]) {
max = target[i];
}
}
for (j = 0; j < n; j++) {
if (min > target[j]) {
min = target[j];
}
}
diff = max - min;
return diff;
}
第6题：
#include
#include
void copy_arr(double x[][5], double source[][5], int n); #注：用数组表示法
void copy_ptr(double(*y)[5], double(*source)[5], int n);#注：指针表示法
int main(void)
{
double target1[2][5];
double target2[2][5];
double source[2][5] = { {1.1,2.2,3.3,4.4,5.5},
{7.7,8.8,9.9,10.1,11.1} };
copy_arr(target1, source, 5);
copy_ptr(target2, source, 5);
return 0;
}
void copy_arr(double x[][5], double source[][5], int n)
{
int i;
int j;
for (i = 0; i < 2; i++) {
putchar('n');
for (j = 0; j < n; j++) {
x[i][j] = source[i][j];
printf("%g ", x[i][j]);
}
}
}
void copy_ptr(double(* y)[5], double(*source)[5], int n)
{
int i,j;
putchar('n');
for (i = 0; i < 2; i++){
putchar('n');
for (j = 0; j < n; j++) {
*(*(y+i) + j) = *(*(source+i) + j);
printf("%g ", *(*(y + i) + j));
}
}
}
第7题：
#include
void copy_ptr(double* y, double source[], int n);
int main(void)
{
double target[3];
double source[] = { 1.1,2.2,3.3,4.4,5.5,6.6,7.7 };
copy_ptr(target, source, 3);
return 0;
}
void copy_ptr(double* y, double source[], int n)
{
int i;
for (i = 0; i < n; i++) {
*(y + i) = *(source + 2 + i);
printf("%g ", *(y + i));
}
}
第8题：
#include
void copy_ptr(double* y, double source[], int n);
int main(void)
{
double target[3];
double source[] = { 1.1,2.2,3.3,4.4,5.5,6.6,7.7 };
copy_ptr(target, source, 3);
return 0;
}
void copy_ptr(double* y, double source[], int n)
{
int i;
for (i = 0; i < n; i++) {
*(y + i) = *(source + 2 + i);
printf("%g ", *(y + i));
}
}
第9题：#注：VS编译器不支持变长数组，所以这题和第7题类似
#include
void copy_arr(int rows, int cols, double ar[][5],double cr[][5]);
int main(void) {
double source[][5] = { {1,2,3,4,5},{5,4,3,2,1},{10,9,8,7,6} };
double target[3][5];
copy_arr(3, 5, source, target);
return 0;
}
void copy_arr(int rows, int cols, double ar[][5], double cr[][5]) {
int i, j;
for (i = 0; i < rows; i++) {
putchar('n');
for (j = 0; j < cols; j++) {
cr[i][j] = ar[i][j];
printf("%g ", cr[i][j]);
}
}
}
第10题：
#include
#define SIZE 4
void get_arr(double ar[], double cr[], int n);
int main(void) {
double ar[] = { 1,5,4,8 };
double cr[] = { 5,5.6,8.3,8.8 };
get_arr(ar, cr, SIZE);
return 0;
}
void get_arr(double ar[], double cr[], int n) {
int i;
double sum_arr[SIZE]; #注：C语言貌似无法直接声明一个空的数组，必须要一个列。
for (i = 0; i < n; i++) {
sum_arr[i] = ar[i] + cr[i];
printf("%g ", sum_arr[i]);
}
}
加油！
