供参考……
#include "stdio.h"
#include "string.h"
void main(){
char Str[120],cx,Letter[][2]={{'A',0},{'B',0},{'C',0},{'D',0},{'E',0},{'F',0},{'G',0},
{'H',0},{'I',0},{'J',0},{'K',0},{'L',0},{'M',0},{'N',0},
{'O',0},{'P',0},{'Q',0},{'R',0},{'S',0},{'T',0},{'U',0},
{'V',0},{'W',0},{'X',0},{'Y',0},{'Z',0}};
int ln,i,j,k;
printf("请输入一个大写字母字符串...nStr=");
ln=strlen(gets(Str));
for(i=0;i