C++辅导 精简版的词法解析器 C讲解 C/C++编程、辅导C/C++程序

日期：2018-09-17 01:27

#include <stdio.h>

#include <stdlib.h>

#include <math.h>

#include <ctype.h>

#include <string.h>

#define CHARCONSTANT '\0'

#define MAXWORDS 10000

#define MAXCHARS 100

typedef char word_t[MAXCHARS+1];

int read_store_word(word_t w_list, int lim);

int stage1(word_t all_words[MAXCHARS], int limit);

int overlap_num(char ss[MAXCHARS], char fragment[MAXCHARS], int idx);

char *overlap_words(char *txt, char *pat);

int

read_store_word(char w_list[], int lim) {

int c, nchar=0;

while ((c=getchar()) != EOF && !isalpha(c)) {

}

if (c==EOF) {

return EOF;

}

w_list[nchar++] = c;

while (nchar < lim && (c=getchar())!= EOF && isalpha(c)) {

w_list[nchar++] = c;

}

w_list[nchar] = CHARCONSTANT;

return 0;

}

int

stage1(char all_words[][MAXCHARS+1], int limit) {

word_t frag[MAXCHARS];

char superstr[MAXCHARS];

int i, index, len_ss;

int fir_index;

strcpy(superstr, all_words[0]);

len_ss = strlen(superstr);

for (i=0; i < limit; i++) {

strcpy(frag[i], all_words[i]);

}

for (i=0; i < limit; i++) {

index = strlen(superstr) - strlen(frag[i]);

if (!overlap_words(superstr, frag[i])) {

if (overlap_num(superstr, frag[i], index)) {

fir_index = len_ss-overlap_num(superstr, frag[i], index);

frag[i][0] = toupper(frag[i][0]);

superstr[fir_index] = '\0';

strcat(superstr, frag[i]);

} else {

frag[i][0] = toupper(frag[i][0]);

strcat(superstr, frag[i]);

}

}

printf("%d: frag=%d, slen=%d %s\n", i, i, strlen(superstr), superstr);

}

return 0;

}

int

overlap_num(char superstring[MAXCHARS], char fragment[MAXCHARS], int idx) {

int j, num=0;

for (j=0; j < strlen(superstring) - idx; j++) {

if (tolower(superstring[idx+j]) == tolower(fragment[j])) {

num = num + 1;

}

if (tolower(superstring[idx+j]) != tolower(fragment[j])) {

idx = idx + 1;

num =0;

break;

}

if (num == strlen(superstring) - idx) {

return num;

}

}

return 0;

}

char *overlap_words(char *txt, char *pat) {

int tl=strlen(txt);

int pl=strlen(pat);

int i;

for (i=0; i<=tl-pl; i++) {

   if (strncasecmp(txt+i, pat, pl)==0) {

return txt+i;

   }

}

return NULL;

   }

int

main(int argc, char *argv[]) {

word_t one_word, all_word[MAXWORDS];

int nwords=0, nfrag=0;

while (read_store_word(one_word, MAXWORDS) != EOF) {

nfrag += 1;

if (nwords < MAXWORDS) {

strcpy(all_word[nwords], one_word);

nwords += 1;

}

}

stage1(all_word, nwords);

return 0;

}