Submission #394956

#	Time	Username	Problem	Language	Result	Execution time	Memory
394956		Qw3rTy	Rabbit Carrot (LMIO19_triusis)	C++11	100 / 100	229 ms	109880 KiB

triusis

#include <bits/stdc++.h>
#define int long long
#define INF 2e9
using namespace std;

const int maxN = 2e5+5;

int f[maxN]; //f[i] = length of longest non-increasing subsequence that ends at b[i]
int a[maxN];
int b[maxN]; //b[i] = a[i] - M * i
int N,M;

struct node{
    int val,lc,rc;
    node(){};
}tree[maxN*100];

int cnt;

void init(){
    cnt = 1;
    tree[cnt].lc = tree[cnt].rc = 0;
    tree[cnt].val = 0;
    return;
}

int build(){
    tree[++cnt].val = 0;
    tree[cnt].lc = 0;
    tree[cnt].rc = 0;
    return cnt;
}

void pushup(int p){
    tree[p].val = max(tree[tree[p].lc].val,tree[tree[p].rc].val);
    return;
}

void update(int p, int l, int r, int a, int b, int val){
    if(a > r || b < l)return;
    if(a <= l && r <= b){
        tree[p].val = max(tree[p].val,val);
        return;
    }
    int mid = (l+r)>>1;
    if(tree[p].lc == 0)tree[p].lc = build();
    if(tree[p].rc == 0)tree[p].rc = build();
    update(tree[p].lc,l,mid,a,b,val);
    update(tree[p].rc,mid+1,r,a,b,val);
    pushup(p);
    return;
}

int query(int p, int l, int r, int a, int b){
    if(p == 0)return 0;
    if(a > r || b < l)return 0;
    if(a <= l && r <= b)return tree[p].val;
    int mid = (l+r)>>1;
    return max(query(tree[p].lc,l,mid,a,b),query(tree[p].rc,mid+1,r,a,b));
}

void testIO(){
    freopen("../test.in","r",stdin);
    return;
}

signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    //testIO();
    cin >> N >> M;
    for(int i = 1; i <= N; ++i)cin >> a[i];
    a[0] = 0;
    f[0] = 0;
    //O(NlogN)
    //find LIS on b[i], where b[i] = a[i] - M*i
    for(int i = 1; i <= N; ++i)b[i] = a[i] - M*i;
    init();
    for(int i = 1; i <= N; ++i){
        if(b[i] > 0)continue;
        f[i] = query(1,-INF,0,b[i],INF) + 1;
        update(1,-INF,0,b[i],b[i],f[i]);
    }
    int res = 0;
    for(int i = 1; i <= N; ++i)res = max(res,f[i]);
    cout << N - res << '\n';
    return 0;
}

Compilation message (stderr)

triusis.cpp: In function 'void testIO()':
triusis.cpp:63:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   63 |     freopen("../test.in","r",stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 14 / 14
• Subtask 2: 21 / 21
• Subtask 3: 28 / 28
• Subtask 4: 37 / 37