#include <bits/stdc++.h>
#define pii pair<int, int>
#define x first
#define y second
using namespace std;
const int N = 2e6 + 5;
pii add(pii a, pii b) { return pii(a.x + b.x, a.y + b.y); }
pii sub(pii a, pii b) { return pii(a.x - b.x, a.y - b.y); }
pii mul(pii a, pii b) { return pii(a.x * b.x, a.y * b.y); }
pii prm(69, 1337);
pii pwr[N];
int n, mid;
pii dp[N];
char A[N];
map<pii, pii> ans;
int main() {
pwr[0] = pii(1, 1);
for(int i = 1; i < N; i++) pwr[i] = mul(pwr[i - 1], prm);
scanf("%d", &n);
if(!(n & 1)) return !printf("NOT POSSIBLE");
mid = n >> 1;
scanf("%s", A + 1);
for(int i = 1; i <= n; i++) dp[i] = add(mul(dp[i - 1], prm), pii(A[i], A[i]));
for(int i = 1; i <= n; i++) {
pii lhs, rhs;
if(i <= mid) {
lhs = add(mul(dp[i - 1], pwr[mid - i + 1]), sub(dp[mid + 1], mul(dp[i], pwr[mid - i + 1])));
rhs = sub(dp[n], mul(dp[mid + 1], pwr[mid]));
if(lhs == rhs && !ans.count(lhs)) ans[lhs] = pii(mid + 2, n);
} else {
lhs = dp[mid];
rhs = add(mul(sub(dp[i - 1], mul(dp[mid], pwr[i - mid - 1])), pwr[n - i]), sub(dp[n], mul(dp[i], pwr[n - i])));
if(lhs == rhs && !ans.count(lhs)) ans[lhs] = pii(1, mid);
}
}
if(!ans.size()) return !printf("NOT POSSIBLE");
else if(ans.size() == 1) for(int i = ans.begin()->y.x; i <= ans.begin()->y.y; i++) printf("%c", A[i]);
else if(ans.size() > 1) return !printf("NOT UNIQUE");
return 0;
}
Compilation message
friends.cpp: In function 'int main()':
friends.cpp:27:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d", &n);
~~~~~^~~~~~~~~~
friends.cpp:30:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%s", A + 1);
~~~~~^~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
16 ms |
16120 KB |
Output is correct |
| 2 |
Correct |
16 ms |
16172 KB |
Output is correct |
| 3 |
Correct |
18 ms |
16304 KB |
Output is correct |
| 4 |
Correct |
17 ms |
16332 KB |
Output is correct |
| 5 |
Correct |
16 ms |
16332 KB |
Output is correct |
| 6 |
Correct |
18 ms |
16416 KB |
Output is correct |
| 7 |
Correct |
16 ms |
16416 KB |
Output is correct |
| 8 |
Correct |
16 ms |
16416 KB |
Output is correct |
| 9 |
Correct |
16 ms |
16416 KB |
Output is correct |
| 10 |
Correct |
18 ms |
16416 KB |
Output is correct |
| 11 |
Correct |
16 ms |
16416 KB |
Output is correct |
| 12 |
Correct |
18 ms |
16420 KB |
Output is correct |
| 13 |
Correct |
16 ms |
16424 KB |
Output is correct |
| 14 |
Correct |
16 ms |
16468 KB |
Output is correct |
| 15 |
Correct |
17 ms |
16548 KB |
Output is correct |
| 16 |
Correct |
16 ms |
16628 KB |
Output is correct |
| 17 |
Correct |
16 ms |
16628 KB |
Output is correct |
| 18 |
Correct |
16 ms |
16628 KB |
Output is correct |
| 19 |
Correct |
16 ms |
16628 KB |
Output is correct |
| 20 |
Correct |
16 ms |
16628 KB |
Output is correct |
| 21 |
Correct |
16 ms |
16644 KB |
Output is correct |
| 22 |
Correct |
16 ms |
16644 KB |
Output is correct |
| 23 |
Correct |
19 ms |
16656 KB |
Output is correct |
| 24 |
Correct |
16 ms |
16656 KB |
Output is correct |
| 25 |
Correct |
16 ms |
16656 KB |
Output is correct |
| 26 |
Correct |
16 ms |
16656 KB |
Output is correct |
| 27 |
Correct |
16 ms |
16656 KB |
Output is correct |
| 28 |
Correct |
19 ms |
16656 KB |
Output is correct |
| 29 |
Correct |
17 ms |
16656 KB |
Output is correct |
| 30 |
Correct |
16 ms |
16656 KB |
Output is correct |
| 31 |
Correct |
16 ms |
16656 KB |
Output is correct |
| 32 |
Correct |
18 ms |
16656 KB |
Output is correct |
| 33 |
Correct |
17 ms |
16656 KB |
Output is correct |
| 34 |
Correct |
17 ms |
16656 KB |
Output is correct |
| 35 |
Correct |
17 ms |
16656 KB |
Output is correct |
| 36 |
Correct |
16 ms |
16656 KB |
Output is correct |
| 37 |
Correct |
16 ms |
16656 KB |
Output is correct |
| 38 |
Correct |
18 ms |
16656 KB |
Output is correct |
| 39 |
Correct |
16 ms |
16656 KB |
Output is correct |
| 40 |
Correct |
17 ms |
16768 KB |
Output is correct |
| 41 |
Correct |
16 ms |
16768 KB |
Output is correct |
| 42 |
Correct |
17 ms |
16768 KB |
Output is correct |
| 43 |
Correct |
16 ms |
16768 KB |
Output is correct |
| 44 |
Correct |
16 ms |
16768 KB |
Output is correct |
| 45 |
Correct |
15 ms |
16768 KB |
Output is correct |
| 46 |
Correct |
16 ms |
16768 KB |
Output is correct |
| 47 |
Correct |
17 ms |
16768 KB |
Output is correct |
| 48 |
Correct |
19 ms |
16768 KB |
Output is correct |
| 49 |
Correct |
17 ms |
16768 KB |
Output is correct |
| 50 |
Correct |
16 ms |
16768 KB |
Output is correct |
| 51 |
Correct |
16 ms |
16768 KB |
Output is correct |
| 52 |
Correct |
16 ms |
16768 KB |
Output is correct |
| 53 |
Correct |
16 ms |
16768 KB |
Output is correct |
| 54 |
Correct |
17 ms |
16856 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
97 ms |
37212 KB |
Output is correct |
| 2 |
Correct |
96 ms |
39224 KB |
Output is correct |
| 3 |
Correct |
99 ms |
41204 KB |
Output is correct |
| 4 |
Correct |
99 ms |
43144 KB |
Output is correct |
| 5 |
Correct |
96 ms |
45244 KB |
Output is correct |
| 6 |
Correct |
16 ms |
45244 KB |
Output is correct |
| 7 |
Correct |
107 ms |
47156 KB |
Output is correct |
| 8 |
Correct |
51 ms |
47156 KB |
Output is correct |
| 9 |
Correct |
90 ms |
48756 KB |
Output is correct |
| 10 |
Correct |
91 ms |
50584 KB |
Output is correct |
| 11 |
Correct |
47 ms |
50584 KB |
Output is correct |
| 12 |
Correct |
21 ms |
50584 KB |
Output is correct |
| 13 |
Correct |
20 ms |
50584 KB |
Output is correct |
| 14 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 15 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 16 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 17 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 18 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 19 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 20 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 21 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 22 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 23 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 24 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 25 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 26 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 27 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 28 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 29 |
Correct |
17 ms |
50584 KB |
Output is correct |
| 30 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 31 |
Correct |
17 ms |
50584 KB |
Output is correct |
| 32 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 33 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 34 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 35 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 36 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 37 |
Correct |
18 ms |
50584 KB |
Output is correct |
| 38 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 39 |
Correct |
17 ms |
50584 KB |
Output is correct |
| 40 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 41 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 42 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 43 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 44 |
Correct |
19 ms |
50584 KB |
Output is correct |
| 45 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 46 |
Correct |
15 ms |
50584 KB |
Output is correct |
| 47 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 48 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 49 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 50 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 51 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 52 |
Correct |
19 ms |
50584 KB |
Output is correct |
| 53 |
Correct |
16 ms |
50584 KB |
Output is correct |
| 54 |
Correct |
16 ms |
50584 KB |
Output is correct |
