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  1. #include <stdio.h>
  2.  
  3. void alternateUpper(char str[]) {
  4.     for (int i = 0; str[i] != '\0'; i++) {
  5.         if (i % 2 == 1) {  // odd index → uppercase
  6.             if (str[i] >= 'a' && str[i] <= 'z')
  7.                 str[i] = str[i] - 32;
  8.         } else {           // even index → lowercase
  9.             if (str[i] >= 'A' && str[i] <= 'Z')
  10.                 str[i] = str[i] + 32;
  11.         }
  12.     }
  13. }
  14.  
  15. int main() {
  16.     char str[100];
  17.  
  18.     printf("Enter a string: ");
  19.     gets(str);
  20.  
  21.     alternateUpper(str);
  22.  
  23.     printf("Changed string: %s", str);
  24.  
  25.     return 0;
  26. }
  27.  
Success #stdin #stdout 0.01s 5292KB
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stdin
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raghav
stdout
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Enter a string: Changed string: rAgHaV
https://ideone.com/WJs7hJ
language:
C (gcc 8.3)
created:
6 days ago
visibility:
public

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