Revision en1, by broly_1033, 2022-01-11 22:58:58

Hey everyone, I was trying ADAUNIQ problem on SPOJ https://www.spoj.com/problems/ADAUNIQ/. I want to solve it using Mo's algorithm with updates, I have written the code. It gives the correct output for the default test case also but gives wrong answer on submission. I tried debugging it but couldn't find any fault. I would be extremely thankful if someone can look at my code. Please note that the question asks for "number of unique elements in a segment", so if a segment is [1, 2, 3, 3] the answer will be 2 (because 1 and 2 occur once) and not 3 (not 1, 2, 3 because 3 occurs twice).

#include<bits/stdc++.h>
using namespace std;

const int N = 2*1e5;

class query {
public:
int id, l, r, res, time;
//    int block;
};
vector<query> qv;
vector<pair<int, int> > updateQueries;

int distinct = 0; // distinct elements in current window
int cnt[N+5]; // stores the frequency

cnt[val]++;
if(cnt[val]==1) distinct++;
if(cnt[val]==2) distinct--;
// we are finding unique values in a range
// if we find duplicate, the kind will no longer be distinct
// not same distinct as in DQUERY
}
void rem(int val) {
cnt[val]--;
if(cnt[val]==0) distinct--;
if(cnt[val]==1) distinct++;
}

void update(vector<int>& v, int i, int x, int y) {

int idx = updateQueries[i].first;
int val = updateQueries[i].second;

int old = v[idx];
v[idx] = val;
updateQueries[i].second = old;

if(idx>=x && idx<=y) {
rem(old);
}
}

int main() {

ios_base::sync_with_stdio(0); cin.tie(NULL);

int n, num_q; cin>>n>>num_q;
vector<int> v(n);
for(int i=0; i<n; i++) cin>>v[i];

int sz = pow(n, 2/3)+1;

for(int i=0; i<num_q; i++) {

int c; cin>>c;
if(c==1) {
int idx, val; cin>>idx>>val;
updateQueries.push_back(make_pair(idx, val));
} else if(c==2) {
query q;
cin>>q.l; cin>>q.r;

q.id = i; q.time = updateQueries.size();
//            q.block = (q.l)/sz;
qv.push_back(q);

}
}

// sort queries
sort(qv.begin(), qv.end(), [&](query a, query b){

if((a.l/sz)==(b.l)/sz){
if((a.r/sz)==(b.r/sz)) return a.time<b.time;
return (a.r/sz)<(b.r/sz);
}
return (a.l/sz)<(b.l/sz);

});

int x = 0, y = 0; // maintain current window, [x, y)
int current_time = 0;
for(int i=0; i<qv.size(); i++) {

// update time
int time = qv[i].time;

while(current_time<time) {
update(v, current_time, x, y);
current_time++;
}
while(current_time>time) {
current_time--;
update(v, current_time, x, y);
}

while(y<=qv[i].r) {
y++;
}
// removing y
while(y>(qv[i].r+1)) {
y--;
rem(v[y]);
}
// removing x
while(x<qv[i].l) {
rem(v[x]);
x++;
}
while(x>qv[i].l) {
x--;
}

qv[i].res = distinct;

}

sort(qv.begin(), qv.end(), [&](query a, query b){
return a.id<b.id;
});

for(int i=0; i<qv.size(); i++) {
cout<<qv[i].res<<'\n';
}

return 0;
}



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en1 broly_1033 2022-01-11 22:58:58 3547 Initial revision (published)