编写一个程序，打印输入中各个字符出现频度的直方图

Question

#include
/* NUM_CHARS should really be CHAR_MAX but K&R haven't covered that at this stage in the book /
#define NUM_CHARS 256
int main(void)
{
int c;
long freqarr[NUM_CHARS + 1];
long thisval = 0;
long maxval = 0;
int thisidx = 0;
for(thisidx = 0; thisidx <= NUM_CHARS; thisidx++)
{
freqarr[thisidx] = 0;
}
while((c = getchar()) != EOF)
{
if(c < NUM_CHARS)
{
thisval = ++freqarr[c];
if(thisval > maxval)
{
maxval = thisval;
}
}
else
{
thisval = ++freqarr[NUM_CHARS];
if(thisval > maxval)
{
maxval = thisval;
}
}
file:///E|/我的下载资料/程序设计/c语言/The_C...guage中文英文答案/C程序设计语言（第二版）课后答案.htm（第 16／246 页）2008-5-15 11:00:46
The C Programming Language Exercise
}
for(thisval = maxval; thisval > 0; thisval--)
{
printf("%4d |", thisval);
for(thisidx = 0; thisidx <= NUM_CHARS; thisidx++)
{
if(freqarr[thisidx] >= thisval)
{
printf("");
}
else if(freqarr[thisidx] > 0)
{
printf(" ");
}
}
printf("\n");
}
printf(" +");
for(thisidx = 0; thisidx <= NUM_CHARS; thisidx++)
{
if(freqarr[thisidx] > 0)
{
printf("-");
}
}
printf("\n ");
for(thisidx = 0; thisidx < NUM_CHARS; thisidx++)
{
if(freqarr[thisidx] > 0)
{
printf("%d", thisidx / 100);
}
}
printf("\n ");
for(thisidx = 0; thisidx < NUM_CHARS; thisidx++)
{
if(freqarr[thisidx] > 0)
{
printf("%d", (thisidx - (100 * (thisidx / 100))) / 10 );
}
}
printf("\n ");
for(thisidx = 0; thisidx < NUM_CHARS; thisidx++)
{
if(freqarr[thisidx] > 0)
{
printf("%d", thisidx - (10 * (thisidx / 10)));
}
}
if(freqarr[NUM_CHARS] > 0)
{
printf(">%d\n", NUM_CHARS);
}
printf("\n");
return 0;
file:///E|/我的下载资料/程序设计/c语言/The_C...guage中文英文答案/C程序设计语言（第二版）课后答案.htm（第 17／246 页）2008-5-15 11:00:46
The C Programming Language Exercise
}
我不明白在编写坐标时，为什么要将thisidx除以100或10来计算

Answer 1

进行坐标变换，要不然图标会显得过大。