Codeforces755D （segment tree，implementation）

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凸多边形切割问题：线段树模拟可以做

优弧与劣弧分两种情况考虑
最后结束点一定是起始点
线段树tree_add需要四个参数，tree_sum需要五个参数
线段树所用空间不超maxn*4

#include <cstdio>#include <cstring>using namespace std;#define maxn 1000005int node[maxn];long long tree[maxn*4];void tree_add(int now,int l,int r,int key){    tree[now]++;    if(l==r) return ;    int mid = (l+r)/2;    if(key>mid)        tree_add(now*2+2,mid+1,r,key);    else        tree_add(now*2+1,l,mid,key);}long long tree_sum(int now,int l,int r,int keyl,int keyr){    if(l==keyl&&r==keyr) return tree[now];    int mid = (l+r)/2;    if(keyl>mid)        return tree_sum(now*2+2,mid+1,r,keyl,keyr);    else if(keyr<=mid)        return tree_sum(now*2+1,l,mid,keyl,keyr);    else        return tree_sum(now*2+1,l,mid,keyl,mid)+tree_sum(now*2+2,mid+1,r,mid+1,keyr);}int main(){    memset(node,0,sizeof(node));    memset(tree,0,sizeof(tree));    int N,k;    scanf("%d%d",&N,&k);    long long ans = 1;    int loc = 0;    int nloc = loc+k;    node[loc] = 1;    while(node[nloc]==0)    {        node[nloc] = 1;        tree_add(0,0,N-1,loc);        tree_add(0,0,N-1,nloc);        ans++;        if(nloc<loc)        {            if(k>N/2)                ans+=tree_sum(0,0,N-1,nloc+1,loc-1);            else            {                ans+=tree_sum(0,0,N-1,0,nloc-1);                if(loc!=N-1)                    ans+=tree_sum(0,0,N-1,loc+1,N-1);            }        }else            if(k>N/2){                if(loc!=0)                    ans += tree_sum(0,0,N-1,0,loc-1);                if(nloc!=N-1)                    ans+=tree_sum(0,0,N-1,nloc+1,N-1);            }else                ans+=tree_sum(0,0,N-1,loc+1,nloc-1);        loc = nloc;        nloc = (nloc+k)%N;        printf("%I64d ",ans);    }    ans++;    if(k>N/2)        ans+=tree_sum(0,0,N-1,1,loc-1);    else        ans+=tree_sum(0,0,N-1,loc+1,N-1);    printf("%I64d\n",ans);    return 0;}

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