pku 1177 pictures (线段树+扫描线+离散化)

最新推荐文章于 2014-09-02 09:36:22 发布

HZXPH

最新推荐文章于 2014-09-02 09:36:22 发布

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分类专栏： ACM 线段树那点事儿文章标签： tree delete insert struct

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本文介绍了一种基于区间覆盖和扫描线算法的实现方法，通过构造特定的数据结构来高效解决涉及线段相交和区域覆盖的问题。文章详细展示了算法的具体实现过程，包括初始化、插入删除操作等关键步骤。

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只能说与pku1151相似，别的还没有发言权

哎~~~~~~~~~~愿自己一路走好！！！！！

代码：

#include<iostream> #include<cstdlib> #include<cmath> #define N 5005 using namespace std; struct elem{ double x; double ly; double ry; bool flag; }; struct node{ int l; int r; int lc,rc; int line; int cover; double m; }; elem cor[2*N]; node tree[8*N]; double index[2*N]; int len; int n; double xres,yres; int cmp(const void *a,const void *b) { if((*(elem *)a).x > (*(elem *)b).x) return 1; else if((*(elem *)a).x == (*(elem *)b).x) return 0; else return -1; } int cmp1(const void *a,const void *b) { if(*(double *)a > *(double *)b) return 1; else if(*(double *)a == *(double *)b) return 0; else return -1; } void init() { int i; int k; double x1,y1,x2,y2; for(i = 0;i < n;i++){ cin >>x1 >>y1 >>x2 >>y2; k = i<<1; cor[k].x = x1; cor[k].ly = y1; cor[k].ry = y2; cor[k].flag = true; cor[k+1].x = x2; cor[k+1].ly = y1; cor[k+1].ry = y2; cor[k+1].flag = false; index[k] = y1; index[k+1] = y2; } qsort(cor,2*n,sizeof(cor[0]),cmp); qsort(index,2*n,sizeof(index[0]),cmp1); len = 0; for(i = 1;i < 2*n;i++){ if(index[i] != index[i-1]) index[++len] = index[i]; } //for(i = 0;i <= len;i++) // cout <<index[i] <<' '; //cout <<endl; return ; } int find(double x) { int mid; int base = 0,top = len; while(base <= top){ mid = (base+top)/2; if(x < index[mid]) top = mid-1; else if(x > index[mid]) base = mid+1; else return mid; } return -1; } void init_m(int k) { int L,R; if(tree[k].cover > 0){ tree[k].m = index[tree[k].r]-index[tree[k].l]; return ; } L = k<<1; R = L+1; if(tree[k].r-tree[k].l > 1){ tree[k].m = tree[L].m+tree[R].m; return ; } tree[k].m = 0; return ; } void init_line(int k) { int L,R; if(tree[k].cover > 0){ tree[k].line = 1; tree[k].lc = 1; tree[k].rc = 1; return ; } L = k<<1; R = L+1; if(tree[k].r-tree[k].l > 1){ tree[k].lc = tree[L].lc; tree[k].rc = tree[R].rc; tree[k].line = tree[L].line+tree[R].line; if(tree[L].rc && tree[R].lc) tree[k].line--; return ; } tree[k].lc = tree[k].rc = 0; tree[k].line = 0; return ; } void buid_tree(int k,int left,int right) { int mid; int L,R; tree[k].l = left; tree[k].r = right; tree[k].cover = 0;tree[k].m = 0; tree[k].line = 0; if(tree[k].r-tree[k].l == 1) return ; mid = (tree[k].l+tree[k].r)/2; L = k<<1; R = L+1; buid_tree(L,left,mid); buid_tree(R,mid,right); return ; } void tree_insert(int k,int left,int right) {//if(k == 1) cout <<left <<' ' <<right <<endl; int mid; int L,R; if(left <= tree[k].l && right >= tree[k].r){ tree[k].cover++; init_m(k); init_line(k); return ; } mid = (tree[k].l+tree[k].r)/2; L = k<<1; R = L+1; if(left < mid) tree_insert(L,left,right); if(right > mid) tree_insert(R,left,right); init_m(k); init_line(k); return ; } void tree_delete(int k,int left,int right) { int mid; int L,R; if(left <= tree[k].l && right >= tree[k].r){ tree[k].cover--; init_m(k); init_line(k); return ; } mid = (tree[k].l+tree[k].r)/2; L = k<<1; R = L+1; if(left < mid) tree_delete(L,left,right); if(right > mid) tree_delete(R,left,right); init_m(k); init_line(k); return ; } int main() { int i; double pre_m; while(cin >>n){ xres = 0; yres = 0; pre_m = 0; init(); buid_tree(1,0,len); for(i = 0;i < (2*n-1);i++){//cout <<cor[i].ly <<' ' <<cor[i].ry <<endl; if(cor[i].flag) tree_insert(1,find(cor[i].ly),find(cor[i].ry)); else tree_delete(1,find(cor[i].ly),find(cor[i].ry)); xres += tree[1].line*(cor[i+1].x-cor[i].x)*2; yres += fabs(tree[1].m-pre_m); pre_m = tree[1].m; } tree_delete(1,find(cor[i].ly),find(cor[i].ry)); yres += fabs(tree[1].m-pre_m); printf("%.0lf/n",yres+xres); } return 0; }