hdu 1162 Eddy's picture（最小產生樹）

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Problem DescriptionEddy begins to like painting pictures recently ,he is sure of himself to become a painter.Every day Eddy draws pictures in his small room, and he usually puts out his newest pictures to let his friends appreciate. but the result it can be imagined, the friends are not interested in his picture.Eddy feels very puzzled,in order to change all friends ‘s view to his technical of painting pictures ,so Eddy creates a problem for the his friends of you.
Problem descriptions as follows: Given you some coordinates pionts on a drawing paper, every point links with the ink with the straight line, causes all points finally to link in the same place. How many distants does your duty discover the shortest length which the ink draws? 
InputThe first line contains 0 < n <= 100, the number of point. For each point, a line follows; each following line contains two real numbers indicating the (x,y) coordinates of the point. 

Input contains multiple test cases. Process to the end of file. 
OutputYour program prints a single real number to two decimal places: the minimum total length of ink lines that can connect all the points.  
Sample Input31.0 1.02.0 2.02.0 4.0 Sample Output3.41

題意：給你N個點的座標，求連通圖的最小距離。

思路：計算每兩個點之間的距離，然後轉化成為暢通工程題。

 1 #include<iostream> 2 #include<stdio.h> 3 #include<string.h> 4 #include<stdlib.h> 5 #include<math.h> 6 #include<algorithm> 7 #define LL long long 8 #define mod 1e9 + 7 9 const int M = 105;10 11 using namespace std;12 13 struct node{14     int x;15     int y;16     double value;17 }a[M * M >> 1];18 19 int cun[M];20 21 double dis(double x1, double y1, double x2, double y2)22 {23     return sqrt(1.0 * (x1 - x2) * (x1 - x2) + 1.0 * (y1 - y2) * (y1 - y2));24 }25 26 bool cmp(node a, node b)27 {28     return a.value < b.value;29 }30 31 int find(int x)32 {33     return cun[x] == x ? x : cun[x] = find(cun[x]);34 }35 36 void shu(int x, int y)37 {38     int p = find(x);39     int q = find(y);40     if(p != q)41         cun[p] = q;42 }43 44 int main()45 {46     int n;47     double s[M], e[M];48     while( cin >> n )49     {50         int temp = 1;51         for(int i = 1; i <= n; ++i)52             cin >> s[i] >> e[i];53         for(int i = 1; i <= n; ++i)54             for(int j = i + 1; j <= n; ++j)55             {56                 a[temp].x = i;57                 a[temp].y = j;58                 a[temp].value = dis(s[i],e[i],s[j],e[j]);59                 temp++;60             }61         for(int i = 0; i <= n; ++i)62             cun[i] = i;63         sort(a,a + temp,cmp);64         double ans = 0;65         for(int i = 1; i < temp; ++i)66         {67             if(find(a[i].x) != find(a[i].y))68             {69                 shu(a[i].x,a[i].y);70                 ans += a[i].value;71             }72         }73         printf("%.2lf\n",ans);74     }75     return 0;76 }

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