pta 编程题16 Saving James Bond - Easy Version

其它pta数据结构编程题请参见：pta

题目

主要用到了深度优先搜索。

 #include <iostream>
 using namespace std;

 struct Vertex
 {
     int x;
     int y;
     bool marked;
 }G[];

 int N; //总鳄鱼数
 int D; //可以跳的距离
 bool dfs(Vertex& v);
 bool firstJump(Vertex v);
 bool jump(Vertex v1, Vertex v2);
 bool success(Vertex v); //可以跳到岸上

 int main()
 {
     int i;
     cin >> N >> D;
     for (i = ; i < N; i++)
         cin >> G[i].x >> G[i].y;

     bool canEscape = false;
     for (i = ; i < N; i++)
     {
         if (!G[i].marked && firstJump(G[i]))
             canEscape = dfs(G[i]);
         if (canEscape) break;
     }
     if (canEscape) cout << "Yes";
     else cout << "No";
     return ;
 }

 bool firstJump(Vertex v)
 {
     return v.x * v.x + v.y * v.y <= ( + D) * ( + D);
 }

 bool dfs(Vertex& v)
 {
     bool canEscape = false;
     v.marked = true;
     if (success(v)) return true;
     for (int i = ; i < N; i++)
     {
         if (!G[i].marked && jump(v, G[i]))
             canEscape = dfs(G[i]);
         if (canEscape) break;
     }
     return canEscape;
 }

 bool success(Vertex v)
 {
     if (v.x <= D -  || v.x >=  - D || v.y <= D -  || v.y >=  - D)
         return true;
     return false;
 }

 bool jump(Vertex v1, Vertex v2)
 {
     return (v1.x - v2.x) * (v1.x - v2.x) + (v1.y - v2.y) * (v1.y - v2.y) <= D*D;
 }