暑假集训-数据结构

求矩形的并 Poj1151

线段树，离散化，扫描线。

  1 #include <iostream>

  2 #include <cstdio>

  3 #include <fstream>

  4 #include <algorithm>

  5 #include <cmath>

  6 #include <deque>

  7 #include <vector>

  8 #include <queue>

  9 #include <string>

 10 #include <cstring>

 11 #include <map>

 12 #include <stack>

 13 #include <set>

 14 #define LL long long

 15 #define INF 0x3f3f3f3f

 16 #define OPEN_FILE

 17 using namespace std;

 18 const int MAXN = 5005;

 19 struct Line{

 20     double left, right;

 21     double y;

 22     int cnt;

 23     Line(){};

 24     Line(double left, double right, double y, int cnt) :left(left), right(right), y(y), cnt(cnt){};

 25 };

 26 bool operator < (Line a, Line b){

 27     return a.y < b.y;

 28 }

 29 struct Node{

 30     double left, right;

 31     int from, to;

 32     int cnt;

 33     double value;

 34 };

 35 int n;

 36 double a[MAXN];

 37 Line scan[MAXN];

 38 Node f[MAXN << 1];

 39 void build(int t, int left, int right){

 40     f[t].left = a[left];

 41     f[t].right = a[right];

 42     f[t].from = left;

 43     f[t].to = right;

 44     f[t].cnt = f[t].value = 0;

 45     if (right - left == 1) return;

 46     int mid = (left + right) >> 1;

 47     build(t << 1, left, mid);

 48     build((t << 1) + 1, mid, right);

 49 }

 50 void update(int t, Line p){

 51     if (p.left == f[t].left && p.right == f[t].right){

 52         f[t].cnt += p.cnt;

 53         if (f[t].cnt > 0){

 54             f[t].value = p.right - p.left;

 55             return;

 56         }

 57         if (f[t].to - f[t].from == 1){

 58             f[t].value = 0;

 59         }

 60         else{

 61             f[t].value = f[t << 1].value + f[(t << 1) + 1].value;

 62         }

 63         return;

 64     }

 65     if (p.left >= f[(t << 1) + 1].left){

 66         update((t << 1) + 1, p);

 67     }

 68     else if (p.right <= f[t << 1].right){

 69         update(t << 1, p);

 70     }

 71     else{

 72         Line q = p;

 73         q.right = f[t << 1].right;

 74         update(t << 1, q);

 75         q = p;

 76         q.left = f[(t << 1) + 1].left;

 77         update((t << 1) + 1, q);

 78     }

 79     if (f[t].cnt > 0){

 80         f[t].value = f[t].right - f[t].left;

 81     }

 82     else{

 83         f[t].value = f[t].to - f[t].from == 1 ?0:f[t << 1].value + f[(t << 1) + 1].value;

 84     }

 85 }

 86 int main()

 87 {

 88 #ifdef OPEN_FILE

 89     //freopen("in.txt", "r", stdin);

 90     //freopen("out.txt", "w", stdout);

 91 #endif // OPEN_FILE

 92     double x1, y1, x2, y2;

 93     int cas = 1;

 94     while (~scanf("%d", &n) && n != 0){

 95         for (int i = 1; i <= n; i++){

 96             scanf("%lf%lf%lf%lf", &x1, &y1, &x2, &y2);

 97             a[i * 2 - 1] = x1;

 98             a[i * 2] = x2;

 99             scan[i * 2 - 1] = Line(x1, x2, y1, 1);

100             scan[i * 2] = Line(x1, x2, y2, -1);

101         }

102         n = n * 2;

103         double ans = 0.0;

104         memset(f, 0, sizeof(f));

105         sort(a + 1, a + n + 1);

106         sort(scan + 1, scan + n + 1);

107         build(1, 1, n);

108         update(1, scan[1]);

109         for (int i = 2; i <= n; i++){

110             ans += f[1].value * (scan[i].y - scan[i - 1].y);

111             update(1, scan[i]);

112         }

113         printf("Test case #%d\nTotal explored area: %.2lf\n\n", cas++, ans);

114     }

115 }

View Code

并查集应用 poj1182

以前对并查集的印象还停留在高中，只是记录一下是不是已经连通。这里加了一个数组rank[i]表示i的秩，也就是到祖先的距离，其实都是高中的内容。

//set

void MakeSet(int x){

    father[x] = x;

    rank[x] = 0;

}

//find

int FindSet(int x)

{

    if (x != father[x])

    {

        father[x] = FindSet(father[x]);

    }

    return father[x];

}

//union

void Union(int x, int y)

{

    x = FindSet(x);

    y = FindSet(y);

    if (x == y) return;

    if (rank[x] > rank[y])

    {

        father[y] = x;

        rank[x] += rank[y];

    }

    else

    {

        if (rank[x] == rank[y])

        {

            rank[y]++;

        }

        father[x] = y;

    }

}