Uva 123 Searching Quickly

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=59

每输入一个句子，将不被忽略的词（not to ignore）及其所在位置保存下来，然后对所有这样的词排序，输出即可。

# include <stdio.h>
# include <string.h>
# include <ctype.h>
# include <stdlib.h>

int n, m;
char ignored[55][15];
char s[205][1005];

int wn;
char words[2005][25];
int pr[2005];
int pc[2005];
int r[2005];

bool exist(char *str)
{
    for (int i = 0; i < n; ++i) {
        if (strcmp(str, ignored[i]) == 0) return true;
    }
    return false;
}

int icmp(const void *x, const void *y) {
    return strcmp( words[*(int*)x], words[*(int*)y] );
}

int main()
{
    n = 0;
    while (1) {
        gets(ignored[n]);
        if (strcmp(ignored[n], "::") == 0) break;
        ++n;
    }
    m = 0;
    wn = 0;
    while (gets(s[m]) != NULL) {
        for (int i = 0; s[m][i]; ++i) s[m][i] = tolower(s[m][i]);
        for (int i = strlen(s[m])-1; s[m][i]==' '; --i) s[m][i] = '';
        char *p = s[m];
        char tmp[25];
        while (1) {
            sscanf(p, "%s", tmp);
            if (exist(tmp) == false) {
                strcpy(words[wn], tmp);
                pr[wn] = m;
                pc[wn] = p-s[m];
                ++wn;
            }
            p += strlen(tmp);
            while (*p == ' ') ++p;
            if (!*p) break;
        }
        ++m;
    }
    for (int i = 0; i < wn; ++i) r[i] = i;
    qsort(r, wn, sizeof(r[0]), icmp);
    for (int i = 0; i < wn; ++i) {
        int k = r[i];
        for (int j = 0; s[pr[k]][j]; ++j) {
            if (j == pc[k]) {
                for (int ii = 0; words[k][ii]; ++ii) {
                    putchar(toupper(words[k][ii]));
                }
                j += strlen(words[k])-1;
            } else putchar(s[pr[k]][j]);
        }
        putchar('
');
    }
    
    return 0;
}