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May 31, 2017 07:57
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Check whether an ascii character is a letter or not.
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| /* | |
| * Thanks to my friend Chrysostomos for the solution. | |
| */ | |
| #include <stdio.h> | |
| int bin_search(int key, int left, int right) | |
| { | |
| while (left <= right) { | |
| int middle = (left + right) / 2; | |
| if (middle < key) left = middle + 1; | |
| else if (middle > key) right = middle - 1; | |
| else return middle; | |
| } | |
| return -1; | |
| } | |
| int main(int argc, char *argv[]) | |
| { | |
| if (argc != 2 || argv[1][1] != '\0') { | |
| puts("Usage: isletter <character>"); | |
| return 1; | |
| } | |
| int ret = bin_search(argv[1][0], 'A', 'Z') | |
| + bin_search(argv[1][0], 'a', 'z'); | |
| if (ret < 0) puts("Not a letter."); | |
| else puts("It is a letter indeed."); | |
| return 0; | |
| } |
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