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Refactor LIS code #13

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Refactor LIS code #13

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4d8ead7
Refactor LIS code
naumazeredo Mar 5, 2021
0ed48f0
Update lis.cpp
samuraiexx Mar 5, 2021
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20 changes: 12 additions & 8 deletions dynamic-programming/lis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3,13 +3,17 @@
// dp(i) = max j<i { dp(j) | a[j] < a[i] } + 1
//

// int dp[N], v[N], n, lis;
int lis(vector<int>& a) {
vector<int> dp (a.size(), 0x3f3f3f3f);
int res = 0;

memset(dp, 63, sizeof dp);
for (int i = 0; i < n; ++i) {
// increasing: lower_bound
// non-decreasing: upper_bound
int j = lower_bound(dp, dp + lis, v[i]) - dp;
dp[j] = min(dp[j], v[i]);
lis = max(lis, j + 1);
for (int v : a) {
// increasing: lower_bound
// non-decreasing: upper_bound
int j = lower_bound(dp.begin(), dp.begin() + res, v) - dp.begin();
dp[j] = min(dp[j], v);
res = max(res, j + 1);
}

return res;
}
9 changes: 5 additions & 4 deletions tests/dynamic-programming/lis.test.cpp
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Expand Up @@ -2,16 +2,17 @@
#include<bits/stdc++.h>
using namespace std;

// @include: dynamic-programming/lis.cpp

const int N = 2e5;

int main() {
int dp[N], v[N], n, lis;
int n;

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

// @include: dynamic-programming/lis.cpp

cout << lis << endl;
cout << lis(v) << endl;
}