I this post we have provided part 3 of the C programs most commonly asked in interview along with answers. We recommend you to try to answer the questions, before referring to the given answer. If you find any mistake or a better alternate solution we are happy to see your suggestions and comments
1. Write a function to trim trailing space
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char * trimr(char *str) { char *end = str + strlen(str) - 1; while(end >= str) { if('\n' == *end || '\t' == *end || '\r' == *end || ' ' == *end) end--; else break; } end[1] = 0; return str; } |
2. Write the implementation of toupper() function
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int toupper(int ch) { if('a' <= ch && ch <= 'z') return 'A' + ch - 'a'; return ch; } |
3. Write the implementation of tolower() function
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int tolower(int ch) { if('A' <= ch && ch <= 'Z') return 'a' + ch - 'A'; return ch; } |
4. Write the implementation of strdup() function
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char * strdup(const char *str) { int len = 0; while(str[len++]); char *dup = (char *)malloc(len); if(NULL == dup) return NULL; char *itr = dup; while(*itr++ = *str++); return dup; } |
5. Write a function to allocate for a 2D int array
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int ** Alloc_2D(int ncol, int nrow) { int **Arr_2D = 0; Arr_2D = (int **)malloc(ncol * sizeof(int *)); if(NULL == Arr_2D) return NULL; for(int r = 0; r < nrow; r++) { Arr_2D[r] = (int *)malloc(nrow * sizeof(int)); if(NULL == Arr_2D[r]) { for(int J = 0; J < I; J++) free(Arr_2D[J]); free(Arr_2D); return NULL; } } return Arr_2D; } |
6. Write a function to reverse the digits of a integer
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int reverse(int num) { int rem = 0; int rev = 0; //while(rem = num % 10) while(num) { rem = num % 10; rev *= 10; rev += rem; num /= 10; } return rev; } |
7. Write the implementation of strtok() function
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char * strtok(char *str, char sep) { static char *pos = 0; static char *cpy = 0; if(str) pos = cpy = str; if(0 == (cpy = pos)) return 0; pos = strchr(pos, sep); if(pos) { pos[0] = 0; pos++; } return cpy; } |
