HDU 1542 Atlantis 矩形面积并

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题目来源：HDU 1542 Atlantis

题意：给你一些矩形（左下角和右上角）求面积

思路：参考here这个超赞的一看就懂了

#include <cstdio>#include <cstring>#include <algorithm>#include <cctype>using namespace std;const int maxn = 210;struct node{double l, r, h;int s, val;node(){}node(double a, double b, double c, int d) : l(a), r(b), h(c), s(d) {} }seg[2*maxn];double sum[maxn<<2];double X[2*maxn];int len[maxn<<2];struct Point{double x;int id, v;}b[2*maxn];bool cmp(node a, node b){return a.h < b.h;}bool cmp1(Point a, Point b){return a.x < b.x;}bool cmp2(Point a, Point b){return a.id < b.id;}void pushup(int rt, int l, int r){if(len[rt])sum[rt] = X[r+1] - X[l];else if(l == r)sum[rt] = 0;elsesum[rt] = sum[rt<<1] + sum[rt<<1|1];}void update(int x, int y, int l, int r, int rt, int c){if(x == l && y == r){len[rt] += c;pushup(rt, l, r);return;}int m = (l + r) >> 1;if(y <= m)update(x, y, l, m, rt<<1, c);else if(x > m)update(x, y, m+1, r, rt<<1|1, c);else{update(x, m, l, m, rt<<1, c);update(m+1, y, m+1, r, rt<<1|1, c);}pushup(rt, l, r); }int main(){int cas = 1;int n;while(scanf("%d", &n) && n){int m = 0, k = 1;for(int i = 0; i < n; i++){double a, b, c, d;scanf("%lf %lf %lf %lf", &a, &b, &c, &d);seg[m++] = node(a, c, b, 1);seg[m++] = node(a, c, d, -1);X[k++] = a;X[k++] = c;}sort(seg, seg+m, cmp);for(int i = 0; i < m; i++){b[i<<1].x = seg[i].l;b[i<<1].id = i<<1;b[i<<1|1].x = seg[i].r;b[i<<1|1].id = i<<1|1;}sort(b, b+2*m, cmp1);int num = 1;double now = b[0].x;for(int i = 0; i < 2*m; i++){if(b[i].x != now){num++;now = b[i].x;}b[i].v = num;}sort(b, b+2*m, cmp2);double s = 0;memset(sum, 0, sizeof(sum));memset(len, 0, sizeof(len));sort(X+1, X+k);k = 1;for(int i = 2; i <= m; i++){if(X[i] != X[i-1])X[++k] = X[i];}for(int i = 0; i < m-1; i++){int l = b[i<<1].v;int r = b[i<<1|1].v-1;if(l <= r)update(l, r, 1, num, 1, seg[i].s);s += sum[1] * (seg[i+1].h - seg[i].h);}printf("Test case #%d\n", cas++);printf("Total explored area: %.2f\n\n", s);}return 0;}

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