i got 0.531 sec for this code
#include <stdio.h>
#include <stdlib.h>

typedef unsigned int type;

struct stack{
    type* value;
    int cnt;
    int size;
};

#define delta 4

#define getnum(num) do {\
    (num) = 0; \
    char c; \
    while(1) { \
        c = fgetc(stdin); \
        if((c<'0')||(c>'9')) break; \
        (num)*=10; \
        (num)+=c-'0'; \
    }\
}while(0)

#define putnum(num) do { \
    char str[16]; \
    char *it = &str[15];*it = 0; \
    if((num)==0) { fputc('0', stdout); } \
    else { \
        while(num) { \
            --it; \
            *it = (char)((num)%10)+'0'; \
            (num)/=10; \
        } \
        while(*it) { \
            fputc(*it, stdout); \
            ++it; \
        } \
    }\
    fputc('\n', stdout); \
} while(0);

struct stack st[1000] = {0};
int main() {
    int cnt;
    getnum(cnt);
    while(cnt--){
        int id;
        char c,i;
        i=0;
        while((c = getchar())!=' ')
            ++i;
        getnum(id);
        --id;
        if(i>3) {
            st[id].cnt++;
            if(st[id].cnt > st[id].size) {
                st[id].size+=delta;
                st[id].value = (type*)realloc(st[id].value,
                                st[id].size*sizeof(type));
            }
            getnum(st[id].value[st[id].cnt-1]);
        }
        else {
            st[id].cnt--;
            putnum(st[id].value[st[id].cnt]);
            if(st[id].cnt+delta<st[id].size) {
                st[id].size-=delta;
                st[id].value = (type*)realloc(st[id].value,
                            st[id].size*sizeof(type));
            }
        }
    }
    return 0;
}

if set delta to 6, then i got MLE on test #12 =/
i broke my brain.
Sorry for my English

у меня точно такой же алгоритм :) и точно такая же проблема :)