hdu - 4347 - The Closest M Points - kd树

来源：互联网发布：三菱4da模块编程实例编辑：程序博客网时间：2024/05/21 17:49
kd树为何物?不知。先放着再说！！！
#include <cstdio>#include <cstring>#include <algorithm>#include <set>using namespace std;const int MAXN = 50010;const int MAXK = 5;const int MAXM = 10;int n, m, k;struct Point{    int p[MAXK];    inline void input()    {        for(int i=0;i<k;++i)        {            scanf("%d", &p[i]);        }    }    inline void output() const    {        for(int i=0;i<k;++i)        {            if(i)            {                printf(" ");            }            printf("%d", p[i]);        }        printf("\n");    }}point[MAXN], searchPoint;int pointSet[16][MAXN];int pointNumber[16];set<Point> ans;inline int getDistance(const Point &a, const Point &b){    int ans = 0;    for(int i=0;i<k;++i)    {        ans += (a.p[i] - b.p[i]) * (a.p[i] - b.p[i]);    }    return ans;}bool operator < (const Point &a, const Point &b){    return getDistance(a, searchPoint) < getDistance(b, searchPoint);}struct TreeNode{    int dim, index;    bool left, right;}tree[MAXN];int sortDimension;bool compare(int x, int y){    return point[x].p[sortDimension] < point[y].p[sortDimension];}bool buildTree(int x, int depth){    int dim = depth % k;    if(pointNumber[depth] == 0)    {        return false;    }    else if(pointNumber[depth] == 1)    {        tree[x].dim = dim;        tree[x].index = pointSet[depth][0];        tree[x].left = false;        tree[x].right = false;        return true;    }    sortDimension = dim;    sort(pointSet[depth], pointSet[depth] + pointNumber[depth], compare);    int mid = pointNumber[depth] >> 1;    tree[x].dim = dim;    tree[x].index = pointSet[depth][mid];    pointNumber[depth + 1] = 0;    for(int i=0;i<mid;++i)    {        pointSet[depth + 1][pointNumber[depth + 1] ++] = pointSet[depth][i];    }    tree[x].left = buildTree(x << 1, depth + 1);    pointNumber[depth + 1] = 0;    for(int i=mid+1;i<pointNumber[depth];++i)    {        pointSet[depth + 1][pointNumber[depth + 1] ++] = pointSet[depth][i];    }    tree[x].right = buildTree((x << 1) + 1, depth + 1);    return true;}#ifndef ONLINE_JUDGEvoid printTree(int x, int depth){    printf("Layer %d: ", depth);    point[tree[x].index].output();    if(tree[x].left)    {        printTree(x << 1, depth + 1);    }    if(tree[x].right)    {        printTree((x << 1) + 1, depth + 1);    }}#endifinline void insertPossibility(const Point &point){    ans.insert(point);    if(ans.size() > m)    {        set<Point>::reverse_iterator it = ans.rbegin();        ans.erase(*it);    }}void queryTree(int x){    insertPossibility(point[tree[x].index]);    if(!tree[x].left && !tree[x].right)    {        return;    }    bool flag = false;    int dist1 = searchPoint.p[tree[x].dim] - point[tree[x].index].p[tree[x].dim];    dist1 *= dist1;    if(searchPoint.p[tree[x].dim] < point[tree[x].index].p[tree[x].dim])    {        if(tree[x].left)        {            queryTree(x << 1);        }        if(tree[x].right)        {            if(ans.size() < m)            {                flag = true;            }            else            {                set<Point>::reverse_iterator it = ans.rbegin();                Point temp = *it;                int dist2 = getDistance(temp, searchPoint);                if(dist1 <= dist2)                {                    flag = true;                }            }            if(flag)            {                queryTree((x << 1) + 1);            }        }    }    else    {        if(tree[x].right)        {            queryTree((x << 1) + 1);        }        if(tree[x].left)        {            if(ans.size() < m)            {                flag = true;            }            else            {                set<Point>::reverse_iterator it = ans.rbegin();                Point temp = *it;                int dist2 = getDistance(temp, searchPoint);                if(dist1 <= dist2)                {                    flag = true;                }            }            if(flag)            {                queryTree(x << 1);            }        }    }}void solve(){    ans.clear();    queryTree(1);}int main(){    int t;    while(~scanf("%d%d",&n,&k))    {        pointNumber[0] = n;        for(int i=0;i<n;++i)        {            point[i].input();            pointSet[0][i] = i;        }        buildTree(1, 0);        #ifndef ONLINE_JUDGE            printTree(1, 0);        #endif        scanf("%d", &t);        while(t--)        {            searchPoint.input();            scanf("%d", &m);            solve();            printf("the closest %d points are:\n", m);            for(set<Point>::iterator it=ans.begin();it!=ans.end();++it)            {                it->output();            }        }    }    return 0;}