cpp_10_1

修改程序清单10.7的rain.c程序，用指针进行计算（仍然要声明并初始化数组）。

//程序清单2.10

#include <stdio.h>
#define MONTHS 12 // 一年的月份数
#define YEARS 5 // 年数
int main(void)
{
// 用2010～2014年的降水量数据初始化数组
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;
printf(" YEAR RAINFALL (inches)\n");
for (year = 0, total = 0; year < YEARS; year++)
{ // 每一年，各月的降水量总和
for (month = 0, subtot = 0; month < MONTHS;month++)
subtot += rain[year][month];
printf("%5d %15.1f\n", 2010 + year, subtot);
total += subtot; // 5年的总降水量
}
printf("\nThe yearly average is %.1f inches.\n\n",total / YEARS);
printf("MONTHLY AVERAGES:\n\n");
printf(" Jan Feb Mar Apr May Jun Jul Aug Sep Oct ");
printf(" Nov Dec\n");
for (month = 0; month < MONTHS; month++)
{ // 每个月，5年的总降水量
for (year = 0, subtot = 0; year < YEARS;year++)
subtot += rain[year][month];
printf("%4.1f ", subtot / YEARS);
}
printf("\n");
return 0;
}

修改后：

#include <stdio.h>
#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=0;
	const float (*ptr)[MONTHS]=rain;
	
	printf(" YEAR RAINFALL (inches)\n");
	
	for(year=0;year<YEARS;year++){
		
		subtot=0;
		
		for(month=0;month<MONTHS;month++){
			
			subtot+=*(*(ptr+year)+month);
			
		}
		
        printf("%5d %15.1f\n", 2010 + year, subtot);
		total+=subtot;
		
	}
	
	printf("\nThe yearly average is %.1f inches.\n\n",total / YEARS);
	printf("MONTHLY AVERAGES:\n\n");
    printf(" Jan Feb Mar Apr May Jun Jul Aug Sep Oct ");
    printf(" Nov Dec\n");
    
    for (month = 0; month < MONTHS; month++){
    	
	    for (year = 0, subtot = 0; year < YEARS;year++){
	    	
	    	subtot += *(*(ptr+year)+month);
            
		}

		printf("%4.1f ", subtot / YEARS);
		
	}

	printf("\n");

	return 0;

}