PAT 1040 Longest Symmetric String

#include <cstdio>
#include <cstdlib>

using namespace std;

char line[1001];
char line2[2003];

int syslen(char str[], int start) {
    int len = 1;
    int p = start - 1;
    int q = start + 1;
    while (p >=0 && str[q] != '\0' && str[p] == str[q]) {
        p--, q++;
        len += 2;
    }
    return len;
}

int main() {
    scanf("%[^\n]s", line);
    
    int p = 0, q = 0;
    line2[p++] = ' ';
    line2[p++] = line[q++];
    while (line[q] != '\0') {
        line2[p++] = ' '; // dummy char used as seperator
        line2[p++] = line[q++];
    }
    line2[p++] = ' ';
    line2[p] = '\0';
    int max_len = 0;
    for (int i=0; i<p; i++) {
        int cur_len = syslen(line2, i);
        if (cur_len > max_len) max_len = cur_len;
    }
    printf("%d", max_len/2);
    return 0;
}

brute force for small case