POJ 1151 統計矩陣的並面積

很快就AC了，後來才發現是POJ數據太弱。（真的是太弱了，表示無奈）多處錯誤都能跑的講。╮(╯▽╰)╭，原來我還是那麼菜—_—

 

參考的薛矛的“算法合集之《剖析線段樹與矩形切割》”，只怪沒好好看，害的另一道題調了好久，等下發出來說下。T_T

#include <cstdio> #include <list> #include <algorithm> using namespace std; struct Rectangle { double x1, y1, x2, y2; bool operator < (const Rectangle& b) { if(x1 != b.x1) { return x1 < b.x1; } else { return y1 < b.y1; } } Rectangle() {} Rectangle(double a, double b, double c, double d) { x1 =a ; y1 = b; x2 = c; y2 = d; } }; list<Rectangle> lst; bool is_intersect(Rectangle a, Rectangle b) { if(b < a) { swap(a, b); } if(b.x1>=a.x1 && b.x1 < a.x2) { if(b.y1 < a.y2) { if(b.y1 >= a.y1) { return true; } else { if(b.y2 > a.y1) { return true; } } } } return false; } void getIntersection(double l1, double r1, double l2, double r2, double& x, double& y) { //這裏保證了有交集 x = max(l1, l2); y = min(r2, r1); } void add(double x1, double y1, double x2, double y2) { lst.push_back(Rectangle(x1, y1, x2, y2)); } void cutAndPush(Rectangle a, Rectangle b) { double x, y, x1, y1; getIntersection(a.x1, a.x2, b.x1, b.x2, x, y); // x is on top-left relative to y if(a.x1 < x) { add(a.x1, a.y1, x, a.y2); } if(a.x2 > y) { add(y, a.y1, a.x2, a.y2); } getIntersection(a.y1, a.y2, b.y1, b.y2, x1, y1); //if(a.y1 < x) { // add(b.x1, a.y1, a.x2, x); //} //if(a.y2 > y) { // add(b.x1, y, a.x2, a.y2); //} if(a.y1 < x1) { add(x, a.y1, y, x1);//add(b.x1, a.y1, a.x2, x1);//add(b.x1, a.y1, b.x2, x1); } if(a.y2 > y1) { add(x, y1, y, a.y2);//add(b.x1, y1, a.x2, a.y2);//add(b.x1, a.y1, b.x2, x1); } } double calArea(Rectangle a) { return (a.x2-a.x1)*(a.y2-a.y1); } int main() { Rectangle r; int n, flag, cas = 1; while(scanf("%d", &n) != EOF && n) { for(int i = 0; i < n; i++) { scanf("%lf%lf%lf%lf", &r.x1, &r.y1, &r.x2, &r.y2); list<Rectangle>::iterator it = lst.begin(), tend = lst.end(); while(it != tend) { if(is_intersect(*it, r)) { cutAndPush(*it, r); //*it is to be cut it = lst.erase(it);//it = lst.erase(*it); } else { it++; } } lst.push_back(r); } double sum = 0.0; for(list<Rectangle>::iterator it = lst.begin(); it != lst.end(); it++) { sum += calArea(*it); } printf("Test case #%d/n", cas++); printf("Total explored area: %.2lf/n/n", sum); lst.clear(); } return 0 ; } 

 

據說經典入門題。。 好吧，算是認識了。