OJ Board

Testcase-wise, using uDebug's Random Input, my code outputted the correct answer. But the OJ stated it as Wrong Answer. What could be wrong here?

#include <iostream>
#include <algorithm>

using namespace std;

int main () {
int n, m;
long hd[20000], kh[20000];
while ( cin >> n >> m && n != 0 ...

Wrong Answer? Already tested this using inputs from uDebug Random Inputs, all clear. Where are the mistakes on this code? (my algorithm is somehow a brute-forced one)

#include <iostream>
#include <cmath>

using namespace std;

int main () {
short p, q, r, s, t, u;
while ( cin >> p >> q >> r >> s ...

I would like to know what caused my code to exceed the time limit. Tested the random input from uDebug and the outputs were fine.

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cmath>

using namespace std;

int main () {
long s, d, n, x[20000], y[20000], i[20000];
// cin ...