65 lines
1.2 KiB
C
65 lines
1.2 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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// max length input string
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#define MAXSTR 25
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// convert input binary string to a number
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int bindec(char*, size_t);
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int main() {
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// user input string
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char s[MAXSTR+3];
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// prompt for input
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printf("> ");
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// read input string; at most MAXSTR+1 chars accepted
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// Note: this is tricky. If we accept only MAXSTR chars,
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// we can't see if user entered more chars and they are
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// being dropped by fgets.
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fgets(s, MAXSTR+3, stdin);
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// check input length; n does not include final carriage return
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int n = strlen(s)-1;
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if (n > MAXSTR) {
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printf("input cannot be more than %d characters\n", MAXSTR);
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exit(1);
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}
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for(size_t i = 0; i < n; i++) {
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if(s[i] == '0' || s[i] == '1') {
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continue;
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}
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else {
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printf("input must contain only zeros and ones\n");
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exit(1);
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}
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}
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if(!n) {
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printf("No input given only hit enter\n");
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exit(1);
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}
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int output = bindec(s, MAXSTR);
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printf("%d\n", output);
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return 0;
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}
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int bindec(char* buf, size_t len) {
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int ret = 0;
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for(size_t i = 0; i < len; i++) {
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if(buf[i] == '1') {
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ret <<= 1;
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ret++;
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}
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else {
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ret <<= 0;
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}
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}
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return ret;
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}
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