PKU 1151 Atlanta (line segment tree + discretization + scanning line)

Not to mention it first, because it is not quite understandable ~~~~~~

# Include <iostream> <br/> # include <cstdlib> <br/> # define N 105 </P> <p> using namespace STD; </P> <p> struct ELEM {<br/> double X; <br/> double S; <br/> double T; <br/> bool flag; <br/>}; </P> <p> struct node {<br/> int L; <br/> int R; <br/> int cover; <br/> double m; <br/>}; </P> <p> ELEM cor [2 * n]; <br/> node tree [8 * n]; <br/> double index [2 * n]; <br/> int Len; <br/> int N; <br/> double res; </P> <p> int CMP (const void * a, const Void * B) <br/>{< br/> If (* (ELEM *) ). x> (* (ELEM *) B ). x) <br/> return 1; <br/> else if (* (ELEM *) ). X = (* (ELEM *) B ). x) <br/> return 0; <br/> else return-1; <br/>}</P> <p> int CMP1 (const void *, const void * B) <br/>{< br/> If (* (double *) A> * (double *) B) <br/> return 1; <br/> else if (* (double *) A = * (double *) B) <br/> return 0; <br/> else return-1; <br/>}</P> <p> void Init () <br/>{< br/> int I; <br/> int K; <Br/> double X1, Y1, X2, Y2; <br/> for (I = 0; I <n; I ++) {<br/> CIN> x1> Y1> X2> Y2; <br/> K = I <1; <br/> cor [K]. X = x1; Cor [K]. S = Y1; Cor [K]. T = Y2; <br/> cor [K]. flag = true; <br/> cor [k + 1]. X = x2; Cor [k + 1]. S = Y1; Cor [k + 1]. T = Y2; <br/> cor [k + 1]. flag = false; <br/> index [k] = Y1; index [k + 1] = Y2; <br/>}< br/> qsort (Cor, 2 * n, sizeof (Cor [0]), CMP); <br/> qsort (index, 2 * n, sizeof (index [0]), CMP1 ); <br/> Len = 0; <br /> For (I = 1; I <2 * n; I ++) {<br/> If (index [I]! = Index [I-1]) <br/> index [+ Len] = index [I]; <br/>}< br/> // for (I = 0; I <= Len; I ++) <br/> // cout <index [I] <''; <br/> // cout <Endl; <br/> return; <br/>}</P> <p> int find (Double X) <br/>{< br/> int base = 0; <br/> int Top = Len; <br/> int mid; // cout <x <''; <br/> while (base <= top) {<br/> mid = (base + TOP)/2; <br/> If (x> index [Mid]) <br/> base = Mid + 1; <br/> else if (x <index [Mid]) <br/> Top = mid-1; <br/> else return mid; <br/>}< br/> return-1; <br/>}</P> <p> void buid_tree (int K, int left, int right) <br/>{< br/> int mid; <br/> int L, R; <br/> tree [K]. L = left; tree [K]. R = right; <br/> tree [K]. cover = 0; tree [K]. m = 0; <br/> If (tree [K]. r-tree [K]. L = 1) <br/> return; <br/> mid = (tree [K]. L + tree [K]. r)/2; <br/> L = k <1; r = L + 1; <br/> buid_tree (L, left, mid ); <br/> buid_tree (R, mid, right); <br/> return; <br/>}</P> <p> void init_m (int K) <br/>{< br/> int L, R; <br/> If (tree [K]. cover> 0) {<br/> tree [K]. M = index [tree [K]. r]-index [tree [K]. l]; <br/> return; <br/>}< br/> L = k <1; r = L + 1; <br/> If (tree [K]. r-tree [K]. l> 1) <br/> tree [K]. M = tree [l]. m + tree [R]. m; <br/> else tree [K]. m = 0; <br/> return; <br/>}</P> <p> void tree_insert (int K, int left, int right) <br/>{< br/> int mid; <br/> int L, R; <br/> If (left <= tree [K]. L & right> = tree [K]. r) {<br/> tree [K]. cover ++; <br/> init_m (k); <br/> return; <br/>}< br/> mid = (tree [K]. L + tree [K]. r)/2; <br/> L = k <1; r = L + 1; <br/> If (left <mid) tree_insert (L, left, right); <br/> If (Right> mid) tree_insert (R, left, right); <br/> init_m (k ); // cout <tree [K]. m <''; <br/> return; <br/>}</P> <p> void tree_delete (int K, int left, int right) <br/>{< br/> int mid; <br/> int L, R; <br/> If (left <= tree [K]. L & right> = tree [K]. r) {<br/> tree [K]. cover --; <br/> init_m (k); <br/> return; <br/>}< br/> mid = (tree [K]. L + tree [K]. r)/2; <br/> L = k <1; r = L + 1; <br/> If (left <mid) tree_delete (L, left, right); <br/> If (Right> mid) tree_delete (R, left, right); <br/> init_m (k); <br/> return; <br/>}</P> <p> void slove () <br/>{< br/> int I; <br/> res = 0; <br/> for (I = 0; I <(2 * N-1); I ++) {<br/> If (Cor [I]. flag) <br/> tree_insert (1, find (Cor [I]. s), find (Cor [I]. t); <br/> else tree_delete (1, find (Cor [I]. s), find (Cor [I]. t); <br/> res + = tree [1]. M * (Cor [I + 1]. x-Cor [I]. x); <br/>}</P> <p> int main () <br/>{< br/> int walk = 0; <br/> while (CIN> N & N) {<br/> Init (); <br/> buid_tree (1, 0, Len ); <br/> slove (); <br/> printf ("Test Case # % d/N", ++ walk); <br/> printf ("total occupied ed area: %. 2lf/n ", Res); <br/>}< br/> return 0; <br/>}