UVALive 6693 - Flow Game（点在线段上判断）

#include <iostream>
#include <string>
#include <cstring>
#include <vector>
#include <cmath>
#include <algorithm>
#include <set>
using namespace std;

int t, n, ans;

struct NODE {
int x, y;

NODE () {}
NODE (int _x, int _y) : x(_x), y(_y) {}

NODE operator - (const NODE& a) const {
return NODE(x - a.x, y - a.y);
}
int cross(const NODE& rhs) const {
return x * rhs.y - y * rhs.x;
}
int dot(const NODE& rhs) const{
return x * rhs.x + y * rhs.y;
}
}node[10];

struct Line {
NODE s, e;

Line() {}
Line(NODE _s, NODE _e) : s(_s), e(_e) {}
int relation(const NODE& rhs) const {
int res = (rhs - s).cross(e - s);
if(res == 0) return 0;
else if(res > 0) return 1;
else return -1;
}
bool point_on_seg(const NODE& rhs) const { //点在线段上的判断
return (rhs - s).cross(e - s) == 0 && (rhs - s).dot(rhs - e) <= 0;
}
};

void print(int add)
{
int ans = 0;
ans = abs(node[1].x - node[0].x) + abs(node[1].y - node[0].y);
ans += abs(node[3].x - node[2].x) + abs(node[3].y - node[2].y) + 2;
if(add != -1) cout << ans + add << endl;
else cout << -1 << endl;
}

int main()
{
cin >> t;
while(t--){
cin >> n;
set<int> sx, sy;
int cnt1 = 0, cnt2 = 2;
for(int i = 1; i <= n; ++i){
char tmp[12];
scanf("%s", tmp + 1);
for(int j = 1; j <= n; ++j){
if(tmp[j] == '1'){
node[cnt1].x = i;
node[cnt1++].y = j;
sx.insert(i), sy.insert(j);
}else if(tmp[j] == '2'){
node[cnt2].x = i;
node[cnt2++].y = j;
sx.insert(i), sy.insert(j);
}
}
}
int ok = 0, flag1 = 0, flag2 = 0, flag3 = 0, flag4 = 0;
Line line1 = Line(node[0], node[1]), line2 = Line(node[2], node[3]);
if(line1.point_on_seg(node[2])) flag1 = 1;
if(line1.point_on_seg(node[3])) flag2 = 1;
if(line2.point_on_seg(node[0])) flag3 = 1;
if(line2.point_on_seg(node[1])) flag4 = 1;

if(flag1 && flag2) {
print(2);
continue;
}
if(flag1 && !flag2) {
cout << -1 << endl;
continue;
}
if(!flag1 && flag2)  {
cout << -1 << endl;
continue;
}
if(flag3 && flag4) {
print(2);
continue;
}
if(flag3 && !flag4) {
cout << -1 << endl;
continue;
}
if(!flag3 && flag4) {
cout << -1 << endl;
continue;
}
int t1 = line1.relation(node[2]), t2 = line1.relation(node[3]);
if(t1 != t2 && t1 && t2) cout << -1 << endl;
else print(0);
}
return 0;
}