uva1606 Amphiphilic Carbon Molecules
2017-11-24 17:11
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题目的主要思想在于依次选定一个节点,然后再选定剩下的另外一个节点,然后判断以这两个节点确定的直线作为边界,相应的黑色节点的个数以及白色节点的个数的最大值,这里也使用了一个很重要的方法,将黑色节点的位置进行中心对称,这样就将求解白色节点以及黑色节点的个数统一起来了,直接求出节点数然后取最大值就行了,具体实现见如下代码:
#include<iostream>
#include<vector>
#include<string>
#include<set>
#include<stack>
#include<queue>
#include<map>
#include<algorithm>
#include<cmath>
#include<iomanip>
#include<cstring>
#include<sstream>
#include<cstdio>
#include<deque>
#include<functional>
using namespace std;
const int maxn = 1005;
int N;
typedef struct node{
double x, y;
double rad;
}node;
bool compare(const node a,const node b){
return a.rad < b.rad;
}
int x[maxn], y[maxn], color[maxn], ans;
bool isLeft(node a,node b){//由a旋转到b
return a.x*b.y - a.y*b.x >= 0;
}
void deal(){
for (int i = 0; i < N; i++){
vector<node> v;
for (int j = 0; j < N; j++){
if (j != i){
node temp;
temp.x = x[j] - x[i];
temp.y = y[j] - y[i];
if (color[j]){
temp.x = -temp.x, temp.y = -temp.y;
}
temp.rad = atan2(temp.y, temp.x);
v.push_back(temp);
}
}
sort(v.begin(), v.end(), compare);
int L = 0, R = 0;
int amount = 2, up = v.size();
while (L < up){
if (L == R){
R = (R + 1) % up;
amount++;
}
while (R != L&&isLeft(v[L], v[R])){
R = (R + 1) % up;
amount++;
}
L++;
amount--;
ans = max(ans, amount);
}
}
}
int main(){
while (cin >> N){
if (N == 0) break;
for (int i = 0; i < N; i++){
cin >> x[i] >> y[i] >> color[i];
}
ans = -1;
deal();
cout << ans << endl;
}
return 0;
}
#include<iostream>
#include<vector>
#include<string>
#include<set>
#include<stack>
#include<queue>
#include<map>
#include<algorithm>
#include<cmath>
#include<iomanip>
#include<cstring>
#include<sstream>
#include<cstdio>
#include<deque>
#include<functional>
using namespace std;
const int maxn = 1005;
int N;
typedef struct node{
double x, y;
double rad;
}node;
bool compare(const node a,const node b){
return a.rad < b.rad;
}
int x[maxn], y[maxn], color[maxn], ans;
bool isLeft(node a,node b){//由a旋转到b
return a.x*b.y - a.y*b.x >= 0;
}
void deal(){
for (int i = 0; i < N; i++){
vector<node> v;
for (int j = 0; j < N; j++){
if (j != i){
node temp;
temp.x = x[j] - x[i];
temp.y = y[j] - y[i];
if (color[j]){
temp.x = -temp.x, temp.y = -temp.y;
}
temp.rad = atan2(temp.y, temp.x);
v.push_back(temp);
}
}
sort(v.begin(), v.end(), compare);
int L = 0, R = 0;
int amount = 2, up = v.size();
while (L < up){
if (L == R){
R = (R + 1) % up;
amount++;
}
while (R != L&&isLeft(v[L], v[R])){
R = (R + 1) % up;
amount++;
}
L++;
amount--;
ans = max(ans, amount);
}
}
}
int main(){
while (cin >> N){
if (N == 0) break;
for (int i = 0; i < N; i++){
cin >> x[i] >> y[i] >> color[i];
}
ans = -1;
deal();
cout << ans << endl;
}
return 0;
}
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