Submission #621270

#	Time	Username	Problem	Language	Result	Execution time	Memory
621270		PoonYaPat	Lightning Rod (NOI18_lightningrod)	C++14	80 / 100	2062 ms	262144 KiB

Main

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

const int MX=10000005;
int n,a[MX],b[MX],pre[MX],pos[MX];
stack<int> st;

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    cin>>n;
    for (int i=1; i<=n; ++i) {
        int x,y;
        cin>>x>>y;
        a[i]=x-y;
        b[i]=x+y;
    }

    for (int i=1; i<=n; ++i) {
        int idx=i-1;
        while (a[i]<=a[idx] && idx>=1) idx=pre[idx];
        pre[i]=idx;
    }

    for (int i=n; i>=1; --i) {
        int idx=i+1;
        while (b[i]>=b[idx] && idx<=n) idx=pos[idx];
        pos[i]=idx;
    }

    st.push(1);
    for (int i=2; i<=n; ++i) {
            //consider point i
        int k=st.top();
        if (pos[k]<=i) {
                //push rod at point i
            while (!st.empty() && pre[i]<=pre[st.top()]) st.pop();
            st.push(i);
        }
    }
    cout<<st.size();
}

• Subtask 1: 4 / 4
• Subtask 2: 7 / 7
• Subtask 3: 12 / 12
• Subtask 4: 21 / 21
• Subtask 5: 26 / 26
• Subtask 6: 10 / 10
• Subtask 7: 0 / 20