uva_327_Evaluating Simple C Expressions

#include <cstdio>
#include <cctype>
#include <cstring>
#include <algorithm>
using namespace std;

#define MAXSPLIT        10
#define MAXVAL          27
#define MAXN            1001

char split[MAXN][MAXSPLIT];
int val_table[MAXVAL], mark[MAXVAL], pos, idx;

void non_space(char *str)
{
char tmp[MAXN];
idx = 0;
for(int i = 0; i < MAXVAL; i ++) {
val_table[i] = i+1;
}
for(int i = 0; i < strlen(str); i ++) {
if( ' ' == str[i] ) {
continue;
}
tmp[idx ++] = str[i];
}
tmp[idx] = '\0'; strcpy(str, tmp);
}

void split_var(const char *str)
{
pos = 0;
for(int i = 0; i < strlen(str); i ++) {
if( !isalpha(str[i]) ) {
continue;
}
if( i >= 2 && (str[i-1] == str[i-2]) && ('+' == str[i-1] || '-' == str[i-1]) ) {
idx = 0;
for(int k = i-2; k <= i; k ++, idx ++) {
split[pos][idx] = str[k];
}
split[pos ++][idx ++] = '\0';

if( i+1 < strlen(str) ) {
split[pos][0] = str[i+1]; split[pos ++][idx ++] = '\0';
}
continue;
}
if( i+2 < strlen(str) && (str[i+1] == str[i+2]) && ('+' == str[i+1] || '-' == str[i+1]) ) {
idx = 0;
for(int k = i; k <= i+2; k ++, idx ++) {
split[pos][idx] = str[k];
}
split[pos ++][idx ++] = '\0';

if( i+3 < strlen(str) ) {
split[pos][0] = str[i+3]; split[pos ++][idx ++] = '\0';
}
continue;
}
split[pos][0] = str[i]; split[pos ++][1] = '\0';
if( i+1 < strlen(str) ) {
split[pos][0] = str[i+1]; split[pos ++][1] = '\0';
}
}
}

int get_expression(const int &index)
{
int rst;
if( strlen(split[index]) > 1 && isalpha(split[index][0]) ) {
rst = val_table[ split[index][0]-'a' ];
val_table[ split[index][0]-'a' ] = ('+' == split[index][1])? rst+1 : rst-1;
}
if( strlen(split[index]) > 1 && !isalpha(split[index][0]) ) {
rst = val_table[ split[index][2]-'a' ];
rst = val_table[ split[index][2]-'a' ] = ('+' == split[index][1])? rst+1 : rst-1;
}
else if( 1 == strlen(split[index]) ) {
rst = val_table[ split[index][0]-'a' ];
}
return rst;
}

int expression_ans(void)
{
int ans(get_expression(0)), l_val, r_val;
for(idx = 1; idx < pos; idx += 2) {
r_val = get_expression(idx+1);
ans = ('+' == split[idx][0])? ans+r_val : ans-r_val;
}
return ans;
}

int main(int argc, char const *argv[])
{
#ifndef ONLINE_JUDGE
freopen("test.in", "r", stdin);
#endif
char str[MAXN];
while( gets(str) > 0 ) {
printf("Expression: %s\n", str);
non_space(str); split_var(str);
printf("    value = %d\n", expression_ans());
memset(mark, 0, sizeof(mark));
for(int i = 0; i < strlen(str); i ++) {
if( isalpha(str[i]) ) {
mark[str[i]-'a'] = 1;
}
}
for(int i = 0; i < MAXVAL; i ++) {
if( mark[i] ) {
printf("    %c = %d\n", i+'a', val_table[i]);
}
}
}
return 0;
}