UVa 00161 - Traffic Lights * (this is a typical situation on the road)

Link: https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=3&page=show_problem&problem=97
Sol:

#include <algorithm>
	#include <cctype>
	#include <cmath>
	#include <cstdio>
	#include <cstring>
	#include <iostream>
	#include <map>
	#include <string>
	#include <vector>
	#define FileIn(file) freopen(file".inp", "r", stdin)
	#define FileOut(file) freopen(file".out", "w", stdout)
	#define FOR(i, a, b) for (int i=a; i<=b; i++)
	#define REP(i, n) for (int i=0; i<n; i++)
	#define Fill(ar, val) memset(ar, val, sizeof(ar))
	#define PI 3.1415926535897932385
	#define uint64 unsigned long long
	#define int64 long long
	#define all(ar) ar.begin(), ar.end()
	#define pb push_back
	#define bit(n) (1<<(n))
	#define Last(i) ( i & -i )
	#define INF 500000000
	#define maxN 105
	using namespace std;
	int n, light[maxN], time_min;
	bool check(int t) {
	FOR (i, 1, n) {
	int m = t / light[i];
	if (m % 2) return false;
	m = t % light[i];
	if (m >= light[i] - 5) return false;
	}
	return true;
	}
	int solve() {
	int t = time_min << 1, g = time_min - 5;
	while (t <= 18000) {
	FOR (i, 0, g)
	if (t + i > 18000) return -1;
	else if (check(t + i)) return t + i;
	t += time_min << 1;
	}
	return -1;
	}
	main() {
	// FileIn("test"); FileOut("test");
	while (scanf("%d", &light[1]) != EOF) {
	if (!light[1]) break;
	n = 1;
	time_min = light[1];
	while (light[n]) {
	scanf("%d", &light[++n]);
	if (light[n]) time_min = min(time_min, light[n]);
	}
	n--;
	int res = solve();
	if (res < 0) puts("Signals fail to synchronise in 5 hours");
	else {
	int h = res / 3600;
	int m = (res - h * 3600) / 60;
	int s = res - h * 3600 - m * 60;
	if (h < 10) printf("0");
	printf("%d:", h);
	if (m < 10) printf("0");
	printf("%d:", m);
	if (s < 10) printf("0");
	printf("%d\n", s);
	}
	}
	scanf("%d %d", &light[2], &light[3]);
	}