CF D. One-Dimensional Battle Ships

一个set水 + 区间判断个数问题。。。。

#include<iostream>#include<cstdio>#include<cstring>#include<set>using namespace std;int L,N,a,M;int main(){    set<int> Pos;    set<int>::iterator it;    cin >> L >> N >> a;    {        Pos.clear();        Pos.insert(0),Pos.insert(L+1);        int ans =1 + (L - a) / (a + 1);        cin >> M;        for(int i = 1; i <= M; ++i)        {            int x;            cin >> x;            it = Pos.lower_bound(x);            int r = *it - 1;            int l = *(--it) + 1;            int len = r - l + 1;            int Sum = 0, SumR = 0, SumL = 0;            if(len >= a)                Sum = 1 + (len - a) / (a + 1);            if(x - l >= a)                SumL = 1 + (x - l - a) / (a + 1);            if(r - x >= a)                SumR = 1 + (r - x - a) / (a + 1);            ans = ans - Sum + SumL + SumR;            if(ans < N) {                cout << i << endl;                return 0;            }            Pos.insert(x);        }        cout << "-1\n";    }    return 0; }