8.1 一维数组
一维数组：用1个组名，存储相同数据类型的数值列表
数组：
数据类型 数组名称［项目个数］
每个数组，都分配了足够的存储区保存在声明语句中给出的数据项的个数
数组中的每一项叫元素element
名为xxx的数组，保留n个什么类型的存储区
#define NUMELS 5
int grades[NUMELS];
element在数组中，被顺序的存储。
通过数组名＋元素的位置，能访问任何单独的元素。
grades[3]
//是存储在grades数组中的第三个元素。
//读作grades 3。
//下标不一定非得是整数，还可能是表达式i, i-1, j+1等
#define NUMELS 5
int total = 0;
for (int i=0, i < NUMELS, i++)
total += grades[i];
#define NUMELS 100
int maximum;
maximum = price[0];
for (int i = 0, i < NUMELS, i++)
if (price[i] > maximum)
maximum = price[i]
数组(名称)保留了(项目个数)个(数据类型(字符/双精度数/整数))的存储区
输入和输出数组
scant("%d %f", &grades[2], &price[3]);
#define NUMELS 5
for (int i = 0, i < NUMELS, i++)
{
printf("Enter grade %d: ", i);
scanf("%d", &grades[i]);
}
#define MAXGRADES 5
#include <stdio.h>
int main()
{
int grades[MAXGRADES];
int i,total = 0;
for (i = 0; i < MAXGRADES; i++) {
printf("Enter grade %d: ", i);
scanf("%d", &grades[i]);
}
for (i = 0; i < MAXGRADES; i++) {
printf("grades %d is %d\n", i, grades[i]);
}
for (i = 0; i < MAXGRADES; i++) {
total += grades[i];
}
printf("The total is %d\n", total);
return 0;
}
8.2 数组初始化
#define SIZE 7
#define NUMGALS 20
double width[SIZE] = {10.96, 6.43, 2.58, .86, 5.89, 7.56, 8.22 };
int gallons[NUMGALS] = {19, 16,
12, 10,
5 };
//初始化数值可以越过多行进行扩展
寻找数组中的最大值
#define MAXELS 5
#include <stdio.h>
int main()
{
int num[MAXELS] = {2, 18, 1, 27, 16};
int i, a, max;
a = 0;
max = num[0];
for (i = 1; i < MAXELS; i++) {
if (max < num[i]) {
max = num[i];
a = i;
}
}
printf("The maximum value is %d %d\n", a, max);
return 0;
}
8.3 数组作为函数参数
找数组中的最大值，使用到了自建函数
#include <stdio.h>
int findMax(int [], int); /* function prototype */
int main()
{
#define MAXELS 5
int nums[MAXELS] = {2, 18, 1, 27, 16};
printf("The maximum value is %d\n", findMax(nums, MAXELS));
return 0;
}
int findMax(int vals[], int numels)
{
int i, max = vals[0];
for (i = 1; i < numels; i++)
if (max < vals[i])
max = vals[i];
return (max);
}
8.4 计算 平均值&标准偏差
#include <stdio.h>
#include <math.h>
double findAvg(int [], int); /* function prototype */
double stdDev(int [], int, double); /* function prototype */
int main()
{
#define NUMELS 10
int values[NUMELS] = {98, 82, 67, 54, 78, 83, 95, 76, 68, 63};
double average, stddev;
average = findAvg(values, NUMELS); /* call the function */
stddev = stdDev(values, NUMELS, average); /* call the function */
printf("The average of the numbers is %5.2f\n", average);
printf("The standard deviation of the numbers is %5.2f\n", stddev);
return 0;
}
double findAvg(int nums[], int numel)
{
int i;
double sumnums = 0.0;
for (i = 0; i < numel; i++) /* calculate the sum of the grades */
sumnums = sumnums + nums[i];
return (sumnums / numel); /* calculate and return the average */
}
double stdDev(int nums[], int numel, double av)
{
int i;
double sumdevs = 0.0;
for (i = 0; i < numel; i++)
sumdevs = sumdevs + pow((nums[i] - av),2);
return(sqrt(sumdevs/numel));
}
8.5 二维、多维数组
二维数组，3行4列
#include <stdio.h>
int main()
{
#define NUMROWS 3//3行
#define NUMCOLS 4//4列
int val[NUMROWS][NUMCOLS] = {8,16,9,52,3,15,27,6,14,25,2,10};
int i, j;
printf("\nDisplay of val array by explicit element");
printf("\n%2d %2d %2d %2d",
val[0][0],val[0][1],val[0][2],val[0][3]);
printf("\n%2d %2d %2d %2d",
val[1][0],val[1][1],val[1][2],val[1][3]);
printf("\n%2d %2d %2d %2d",
val[2][0],val[2][1],val[2][2],val[2][3]);
printf("\n\nDisplay of val array using a nested for loop");
for (i = 0; i < NUMROWS; i++)
{
printf("\n"); /* start a new line for each row */
for (j = 0; j < NUMCOLS; j++)
printf("%2d ", val[i][j]);
}
printf("\n");
return 0;
}
二维数组每个元素x10
#include <stdio.h>
int main()
{
#define NUMROWS 3
#define NUMCOLS 4
int val[NUMROWS][NUMCOLS] = {8,16,9,52,3,15,27,6,14,25,2,10};
int i, j;
/* multiply each element by 10 and display it */
printf("\nDisplay of multiplied elements\n");
for (i = 0; i < NUMROWS; i++)
{
printf("\n"); /* start a new line */
for (j = 0; j < NUMCOLS; ++j)
{
val[i][j] = val[i][j] * 10;
printf("%3d ", val[i][j]);
} /* end of inner loop */
} /* end of outer loop */
printf("\n");
return 0;
}
利用自建函数
#include <stdio.h>
#define ROWS 3
#define COLS 4
void display(int [ROWS][COLS]); /* function prototype */
int main()
{
int val[ROWS][COLS] = {8,16,9,52,
3,15,27,6,
14,25,2,10};
display(val);
return 0;
}
void display(int nums[ROWS][COLS])
{
int rowNum, colNum;
for (rowNum = 0; rowNum < ROWS; rowNum++)
{
for(colNum = 0; colNum < COLS; colNum++)
printf("%4d",nums[rowNum][colNum]);
printf("\n");
}
}
验证元素地址
#include <stdio.h>
#define NUMELS 20
int main()
{
int numbers[NUMELS];
printf("The starting address of the numbers array is: %d\n",
&(numbers[0]));
printf("The storage size of each array element is: %d\n",
sizeof(int));
printf("The address of element numbers[5] is : %d\n", &(numbers[5]));
printf("The starting address of the array,\n");
printf(" using the notation numbers, is: %d\n", numbers);
return 0;
}
语法
数组声明：
数据类型 数组名称［项目个数］
#define NUMELS 5//在声明数组之前，定义数组项目个数为一个符号常量
int grades[NUMELS];//一维
#define ROWS 3
#define COLS 4
int val[ROWS][COLS];//二维
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