#include <bits/stdc++.h>
#define all(dataStructure) dataStructure.begin(),dataStructure.end()
#define ll long long
using namespace std;
namespace std {
template <typename T, int D>
struct _vector : public vector <_vector <T, D - 1>> {
static_assert(D >= 1, "Dimension must be positive!");
template <typename... Args>
_vector(int n = 0, Args... args) : vector <_vector <T, D - 1>> (n, _vector <T, D - 1> (args...)) {}
};
// _vector <int, 3> a(n, m, k);: int a[n][m][k].
// _vector <int, 3> a(n, m, k, x);: int a[n][m][k] initialized with x.
template <typename T>
struct _vector <T, 1> : public vector <T> {
_vector(int n = 0, const T& val = T()) : vector <T> (n, val) {}
};
}
const int MAX = 3e4 + 3;
const ll MOD[] = {1000000007, 998244353};
int n, m;
int b[MAX], p[MAX];
int dp[MAX];
set <int> f[MAX];
void Solve() {
memset(dp, 0x0f, sizeof dp);
cin >> n >> m;
for (int i = 0; i < m; i++) {
cin >> b[i] >> p[i];
f[b[i]].insert(p[i]);
}
priority_queue <pair <int, int>> q;
dp[b[0]] = 0;
q.push({0, b[0]});
while (q.size()) {
auto [D, u] = q.top();
q.pop();
D = -D;
if (D != dp[u]) continue;
if (u == 1) return void(cout << D);
for (auto p : f[u]) {
for (int v = u + p; v < n; v += p) {
if (dp[v] > D + (v - u) / p) {
dp[v] = D + (v - u) / p;
q.emplace(-dp[v], v);
}
if (f[v].count(p)) continue;
}
for (int v = u - p; v >= 0; v -= p) {
if (dp[v] > D + (u - v) / p) {
dp[v] = D + (u - v) / p;
q.emplace(-dp[v], v);
}
if (f[v].count(p)) continue;
}
}
}
cout << -1;
}
int32_t main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
#define TASK "TASK"
if (fopen(TASK".INP", "r")) {
freopen(TASK".INP", "r", stdin);
freopen(TASK".OUT", "w", stdout);
}
/* int TEST = 1; cin >> TEST; while (TEST--) */ Solve();
cerr << "\nTime elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << "s\n";
return 0;
}
Compilation message
skyscraper.cpp: In function 'int32_t main()':
skyscraper.cpp:72:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
72 | freopen(TASK".INP", "r", stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
skyscraper.cpp:73:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
73 | freopen(TASK".OUT", "w", stdout);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
1884 KB |
Output is correct |
2 |
Incorrect |
1 ms |
1884 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
1884 KB |
Output is correct |
2 |
Incorrect |
1 ms |
1884 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
1884 KB |
Output is correct |
2 |
Incorrect |
1 ms |
1884 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
1884 KB |
Output is correct |
2 |
Incorrect |
1 ms |
1884 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
1884 KB |
Output is correct |
2 |
Incorrect |
1 ms |
1880 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |