Enter text and sort alphabetically - c

Question

#include <stdio.h>
#include <string.h>
#include <ctype.h>
int main() {
char str1[100];
char str2[100];
char str3[100];
int count, tmp;
int i, j=0, k=0;
scanf("%s", str1);
count=strlen(str1);
for(i=0; i<count; i++) {
if(islower(str1[i])) {
str2[j]=str1[i];
j++;
}
else if(isupper(str1[i])) {
str3[k]=str1[i];
k++;
}
}
str2[j]='\0';
str3[k]='\0';
for(i=0; i<strlen(str2); i++) {
for(j=0; j<i; j++) {
if(str2[j]>str2[j+1]) {
tmp=str2[j];
str2[j]=str2[j+1];
str2[j+1]=tmp;
}
}
}
for(i=0; i<strlen(str3); i++) {
for(j=0; j<i; j++) {
if(str3[j]>str3[j+1]) {
tmp=str3[j];
str3[j]=str3[j+1];
str3[j+1]=tmp;
}
}
}
printf("lowercase alignment : %s\n", str2);
printf("uppercase alignment : %s", str3);
return 0;
}
I want to get a string input, divide it into uppercase and lowercase letters, and print it out in alphabetical order. However, errors continue to occur during the sorting process. Why did you do that?

Answer 1

I believe the problem is here:
for (i = 0; i < strlen(str2); i++) {
for (j = 0; j < i; j++) {
For this type of sort, I believe this should be:
for (i = 0; i < strlen(str2); i++) {
for (j = 0; j < strlen(str2) - 1; j++) {
That is, the outer loop needs to be done strlen(str2) times, but its i iteration variable should have no effect on the inner loop which needs to walk (nearly) the entire string on each iteration. Thus the inefficiency of this sort method. Ditto the same looping construct that sorts str3.
My rework of your code:
#include <stdio.h>
#include <string.h>
#include <ctype.h>
int main() {
char mixedcase[100];
char lowercase[100];
char uppercase[100];
scanf("%s", mixedcase);
size_t length = strlen(mixedcase);
int l = 0, u = 0;
for (int i = 0; i < length; i++) {
char c = mixedcase[i];
if (isalpha(c)) {
if (islower(c)) {
lowercase[l++] = mixedcase[i];
} else {
uppercase[u++] = mixedcase[i];
}
}
}
lowercase[l] = '\0';
uppercase[u] = '\0';
length = strlen(lowercase);
for (int i = 0; i < length; i++) {
for (int j = 0; j < length - 1; j++) {
if (lowercase[j] > lowercase[j+1]) {
char tmp = lowercase[j];
lowercase[j] = lowercase[j+1];
lowercase[j+1] = tmp;
}
}
}
length = strlen(uppercase);
for (int i = 0; i < length; i++) {
for (int j = 0; j < length - 1; j++) {
if (uppercase[j] > uppercase[j+1]) {
char tmp = uppercase[j];
uppercase[j] = uppercase[j+1];
uppercase[j+1] = tmp;
}
}
}
printf("Lowercase alignment: %s\n", lowercase);
printf("Uppercase alignment: %s\n", uppercase);
return 0;
}
The next thing to do would be to move your sort logic into its own function and call that function on each of the strings to be sorted rather than repeat the code twice in the body of main().