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unordered_map sometimes better than map:

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got TLE with map on Collecting_Numbers_II.cpp but AC with unordered_map
-unordered is good for a lot of requests and a lot of data
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DarianTr
2024-06-04 16:41:13 +02:00
parent 7fd24571df
commit 3bd1aab755
5 changed files with 110 additions and 1 deletions
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39
CSES - CSES Problem Set/Collecting_Numbers_II.cpp Normal file
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// Collecting Numbers II
#include<bits/stdc++.h>
using namespace std;
int main() {
int n; cin >> n;
int m; cin >> m;
vector<int> in(n);
for (auto &e: in) cin >> e;
int count = 1;
unordered_map<int, int> pos;
for (int i{}; i < n; i++) pos[in[i]] = i;
for (int i = 1; i < n; i++) {
if (pos[i] > pos[i+1]) count ++;
}
// cout << count << endl;
for (int i{}; i < m; i++) {
int a, b; cin >> a >> b;
if (in[a - 1] > 1 && pos[in[a - 1] - 1] > a - 1 && pos[in[a - 1] - 1] <= b - 1) count--;
if (in[a - 1] > 1 && pos[in[a - 1] - 1] < a - 1 && pos[in[a - 1] - 1] >= b - 1) count++;
if (in[a - 1] < n && pos[in[a - 1] + 1] > a - 1 && pos[in[a - 1] + 1] <= b - 1) count++; //
if (in[a - 1] < n && pos[in[a - 1] + 1] < a - 1 && pos[in[a - 1] + 1] >= b - 1) count--;
if (in[b - 1] > 1 && pos[in[b - 1] - 1] > a - 1 && pos[in[b - 1] - 1] < b - 1) count++;
if (in[b - 1] > 1 && pos[in[b - 1] - 1] < a - 1 && pos[in[b - 1] - 1] > b - 1) count--;
if (in[b - 1] < n && pos[in[b - 1] + 1] > a - 1 && pos[in[b - 1] + 1] < b - 1) count--;
if (in[b - 1] < n && pos[in[b - 1] + 1] < a - 1 && pos[in[b - 1] + 1] > b - 1) count++;
pos[in[a - 1]] = b - 1;
pos[in[b - 1]] = a - 1;
swap(in[a-1], in[b-1]);
cout << count << endl;
}
return 0;
}