HDU 3803

线段相交模板

#include <iostream>using namespace std;typedef __int64 Lint;struct Point{ Lint x, y;};struct Fract{ Lint z, m; Lint gcd(Lint a, Lint b) { while (b) { Lint r = a % b; a = b; b = r; } return a; } void Create(Lint a, Lint b = 1) { Lint t = gcd(a, b); a = a / t; b = b / t; z = a; m = b; if (m < 0) { m = -m; z = -z; } } void print() { if (m == 1) { printf("%I64d", z); } else { printf("%I64d/%I64d", z, m); } }};int Cmp(const Lint &v){ if (v > 0) return 1; else if (v == 0) return 0; else return -1;}Lint Det(const Point &a, const Point &b, const Point &c){ return (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);}bool Between(const Point &a, const Point &b, const Point &c){ if (a.x - b.x != 0) { Lint mi = min(a.x, b.x); Lint mx = max(a.x, b.x); return mi <= c.x && c.x <= mx; } else { Lint mi = min(a.y, b.y); Lint mx = max(a.y, b.y); return mi <= c.y && c.y <= mx; }}// 0无交点，1有一个交点，2有无数交点// 如果有一个交点，则p为交点位置int Cross(const Point &a, const Point &b, const Point &c, const Point &d, Fract &x, Fract &y){ int k1, k2, k3, k4; Lint s1, s2, s3, s4; k1 = Cmp(s1 = Det(a, b, c)); k2 = Cmp(s2 = Det(a, b, d)); k3 = Cmp(s3 = Det(c, d, a)); k4 = Cmp(s4 = Det(c, d, b)); // 规范相交 if ((k1 ^ k2) == -2 && (k3 ^ k4) == -2) { x.Create(c.x * s2 - d.x * s1, s2 - s1); y.Create(c.y * s2 - d.y * s1, s2 - s1); return 1; } Lint mi1, mx1, mi2, mx2; if (a.x - b.x != 0) { mi1 = min(a.x, b.x); mx1 = max(a.x, b.x); mi2 = min(c.x, d.x); mx2 = max(c.x, d.x); } else { mi1 = min(a.y, b.y); mx1 = max(a.y, b.y); mi2 = min(c.y, d.y); mx2 = max(c.y, d.y); } // 不规范相交 if (k1 == 0 && k2 == 0 && k3 == 0 && k4 == 0) { // 有无数交点 if (mi2 < mi1 && mi1 < mx2 || mi2 < mx1 && mx1 < mx2 || mi1 < mi2 && mi2 < mx1 || mi1 < mx2 && mx2 < mx1 || mi1 <= mi2 && mx2 <= mx1 || mi2 <= mi1 && mx1 <= mx2) { return 2; } } if (k1 == 0 && Between(a, b, c)) { x.Create(c.x); y.Create(c.y); return 1; } if (k2 == 0 && Between(a, b, d)) { x.Create(d.x); y.Create(d.y); return 1; } if (k3 == 0 && Between(c, d, a)) { x.Create(a.x); y.Create(a.y); return 1; } if (k4 == 0 && Between(c, d, b)) { x.Create(b.x); y.Create(b.y); return 1; } return 0;}bool IsPoint(const Point &a, const Point &b){ if (a.x == b.x && a.y == b.y) return true; else return false;}int main(){ int test, cas; Point a, b, c, d; Fract x, y; int res; scanf("%d", &test); for (cas = 1; cas <= test; cas++) { scanf("%I64d %I64d %I64d %I64d", &a.x, &a.y, &b.x, &b.y); scanf("%I64d %I64d %I64d %I64d", &c.x, &c.y, &d.x, &d.y); if (IsPoint(a, b) && IsPoint(c, d)) { if (IsPoint(a, c)) { printf("1/n"); printf("%I64d %I64d/n", a.x, a.y); } else { printf("0/n"); } continue; } if (IsPoint(a, b)) { if (Cmp(Det(c, d, a)) == 0 && Between(c, d, a)) { printf("1/n"); printf("%I64d %I64d/n", a.x, a.y); } else { printf("0/n"); } continue; } if (IsPoint(c, d)) { if (Cmp(Det(a, b, c)) == 0 && Between(a, b, c)) { printf("1/n"); printf("%I64d %I64d/n", c.x, c.y); } else { printf("0/n"); } continue; } res = Cross(a, b, c, d, x, y); if (res == 1) { printf("1/n"); x.print(); printf(" "); y.print(); printf("/n"); } else if (res == 0) { printf("0/n"); } else { printf("INF/n"); } } return 0;}