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Progressive hints first, then the full explanation and implementation when you're ready to cash out.
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Hints
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For a min = k constraint, every position in that interval is forced to be at least . Mark the union of all such intervals.
A marked position can never contain any value below , so it cannot help a MEX- segment contain .
Look at any MEX- interval. Since a valid answer exists, it must contain at least unmarked positions, because the required values all need separate unmarked spots.
List all unmarked positions from left to right and write on them. Any interval sees a consecutive block of this list, so if it has at least unmarked positions, it sees every value through .
For marked positions, output if the position lies inside any MEX constraint, otherwise output . Existence guarantees every min = k interval has at least one marked position outside all MEX intervals, so it gets its exact .
The trick is to stop treating the queries like separate little puzzles. They share positions, so trying to satisfy each range independently gets messy fast. Instead, classify positions by what they are forced to be.
What min = k really says
For a constraint , we need:
So first mark every position that appears in at least one type-1 range. Call these positions forced-high.
Any forced-high position must be in every valid array. That means it can never be one of .
What MEX = k really says
For a constraint , the segment must:
Values bigger than are harmless. They are basically decorative junk food: allowed, but not useful.
Now combine this with forced-high positions. If a forced-high position lies inside a MEX range, it cannot help provide , because it must be . Also, it cannot be exactly , because MEX- ranges must not contain . So such a position should just be .
The main construction
Mark two things:
high[i]: position belongs to some type-1 range;in_mex[i]: position belongs to some type-2 range.Now assign values like this:
high[i] is false, put values cyclically by the order of unmarked positions:
high[i] is true and in_mex[i] is true, set .high[i] is true and in_mex[i] is false, set .That's the whole thing. Very 1400-ish: once you see the classification, the monster was cardboard.
Why every MEX constraint works
Take any type-2 interval .
First, it contains no :
in_mex = true, so they get .So is absent.
Now we need all values to appear.
Because the input is guaranteed valid, this interval must be able to contain those values somehow. But forced-high positions cannot hold values below . Therefore, in any valid array, the values must all be placed on unmarked positions inside . That requires at least unmarked positions in the interval.
Look at the global list of all unmarked positions from left to right. The unmarked positions inside any interval form a consecutive chunk of this list. We colored that list cyclically modulo . Any consecutive chunk of length at least contains every residue .
So every MEX range gets all small values and no . Done.
Why every minimum constraint works
Take any type-1 interval .
Every position in this interval was marked high, so every assigned value there is either or . Therefore the minimum is at least .
We still need the minimum to be exactly , not everywhere.
Suppose this interval had no position outside all MEX constraints. Then every position in it would belong to some type-2 interval. But a type-1 interval needs at least one position equal to , while any position inside a type-2 interval is forbidden from being . Contradiction. Since the statement guarantees a valid array exists, every type-1 interval has at least one marked position not inside any MEX interval.
Our construction assigns exactly to all such positions. So the minimum is exactly .
Complexity
We mark intervals directly. With , this is tiny:
per test case, with memory.
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
void setIO() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
}
int main() {
setIO();
int T;
cin >> T;
while (T--) {
int n, k, q;
cin >> n >> k >> q;
vector<int> high(n, 0), in_mex(n, 0);
for (int i = 0; i < q; i++) {
int c, l, r;
cin >> c >> l >> r;
--l, --r;
if (c == 1) {
for (int j = l; j <= r; j++) high[j] = 1;
} else {
for (int j = l; j <= r; j++) in_mex[j] = 1;
}
}
vector<int> a(n);
int ptr = 0;
for (int i = 0; i < n; i++) {
if (!high[i]) {
a[i] = ptr % k;
ptr++;
} else {
a[i] = in_mex[i] ? k + 1 : k;
}
}
for (int i = 0; i < n; i++) {
if (i) cout << ' ';
cout << a[i];
}
cout << '\n';
}
}#include <bits/stdc++.h>
using namespace std;
using ll = long long;
void setIO() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
}
int main() {
setIO();
int T;
cin >> T;
while (T--) {
int n, k, q;
cin >> n >> k >> q;
vector<int> high(n, 0), in_mex(n, 0);
for (int i = 0; i < q; i++) {
int c, l, r;
cin >> c >> l >> r;
--l, --r;
if (c == 1) {
for (int j = l; j <= r; j++) high[j] = 1;
} else {
for (int j = l; j <= r; j++) in_mex[j] = 1;
}
}
vector<int> a(n);
int ptr = 0;
for (int i = 0; i < n; i++) {
if (!high[i]) {
a[i] = ptr % k;
ptr++;
} else {
a[i] = in_mex[i] ? k + 1 : k;
}
}
for (int i = 0; i < n; i++) {
if (i) cout << ' ';
cout << a[i];
}
cout << '\n';
}
}