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  1.  
  2. #include <stdio.h>
  3.  
  4. void printSubstring(char *start, int len) {
  5.     char *p = start;
  6.     while (len--) {
  7.         putchar(*p);
  8.         p++;
  9.     }
  10.     putchar('\n');
  11. }
  12.  
  13. char* longestUniqueSubstring(char *s, int *outLen) {
  14.     char *start = s;
  15.     char *end = s;
  16.  
  17.     char *bestStart = s;
  18.     int bestLen = 0;
  19.  
  20.     while (*end != '\0') {
  21.  
  22.         // check duplicate of *end in [start, end)
  23.         char *p = start;
  24.         while (p < end) {
  25.             if (*p == *end) {
  26.                 // move start just after previous occurrence
  27.                 start = p + 1;
  28.                 break;
  29.             }
  30.             p++;
  31.         }
  32.  
  33.         int len = (end - start) + 1;
  34.         if (len > bestLen) {
  35.             bestLen = len;
  36.             bestStart = start;
  37.         }
  38.  
  39.         end++;
  40.     }
  41.  
  42.     *outLen = bestLen;
  43.     return bestStart;
  44. }
  45.  
  46. int main() {
  47.     char str[] = "abcab p q r pqbcbb";
  48.  
  49.     int len = 0;
  50.     char *res = longestUniqueSubstring(str, &len);
  51.  
  52.     printf("Longest substring = ");
  53.     printSubstring(res, len);
  54.  
  55.     return 0;
  56. }
Success #stdin #stdout 0s 5320KB
comments (?)
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Standard input is empty
stdout
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Longest substring = r pqbc
https://ideone.com/4rbKgs
language:
C (gcc 8.3)
created:
13 hours ago
visibility:
public

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