分治法解决凸包问题

#include

typedef struct {

int x,y;

}Point;

int arrayLength=0;

int main()

{

printf("**************软件工程3班**************");

printf("*****************成冠辉*****************");

Point array[15],result[15];

InitialData(array);

printf("请输入数据：\n\n");

Put(array,arrayLength);

Qsort(array,0,arrayLength-1);

printf("排序后：\n");

Put(array,arrayLength);

GetResult(array,result);

printf("结果集为：\n");

Put(result,resultCount);

getchar();

return 0;

}

//返回分裂位置

int Partition(Point *array,int l,int r)

{

int p=l,i=l,j=r+1;

do

{

do

{

i++;

}while(array[i].x

do

{

j--;

}while(array[j].x>array[p].x);

swap(array,i,j);

}while(i

swap(array,i,j);

swap(array,p,j);

return j;

}

//用快排将x坐标的值从大到小

void Qsort(Point *array,int l,int r)

{

int s=0;

if(l

{

s=Partition(array,l,r); //分裂位置

Qsort(array,l,s-1);

Qsort(array,s+1,r);

}

}

//打印

void Put(Point *array,int length)

{

for(int i=0;i

{

printf("%d\t%d\n",array[i].x,array[i].y);

}

printf("\n");

}

void GetResult(Point *array,Point *result)

{

Add(array,result); //将首尾两个点并入result[15]

DealWithLeft(0,14,array,result); //处理array[0]->array[14]射线左边的点DealWithLeft(14,0,array,result); //处理array[14]->array[0]射线右边的点}

void InitialData(Point *array)

{

FILE *fp=freopen("input.txt","r",stdin);

char ch;

Point* currentPoint=array;

for(int i=0;ch!=EOF;i++)

{

scanf("%d%d",&array[i].x,&array[i].y);

ch=fgetc(fp);

arrayLength++;

}

fclose(fp);

}

void swap(Point *array,int i,int j)

{

if(i

{

int x=0,y=0;

x=array[i].x;

y=array[i].y;

array[i].x=array[j].x;

array[i].y=array[j].y;

array[j].x=x;

array[j].y=y;

}

}

int resultCount=0; //插入值的个数

void Add(Point *array,Point *result)

{

result[resultCount].x=array[0].x;

result[resultCount++].y=array[0].y;

result[resultCount].x=array[14].x;

result[resultCount++].y=array[14].y;

}

void Add(Point *array,Point *result,int i)

{

result[resultCount].x=array[i].x;

result[resultCount++].y=array[i].y;

}

//处理array[first]->array[final]射线左侧的点

void DealWithLeft(int first,int final,Point *array,Point *result)

{

int max=0,index=-1;

int i=first;

if(firstarray[final]射线左侧

{

for(i;i

{

int x1 = array[first].x,y1 = array[first].y;

int x2 = array[final].x,y2 = array[final].y;

int x3 = array[i].x,y3 = array[i].y;

int compute = x1*y2 + x3*y1 + x2*y3 - x3*y2 - x2*y1 - x1*y3;

if(compute > max)

{

max = compute;

index = i;

}

}

}

else

{

for(i;i>=0;i--)//array[final]->array[first]射线左侧

{

int x1 = array[first].x,y1 = array[first].y;

int x2 = array[final].x,y2 = array[final].y;

int x3 = array[i].x,y3 = array[i].y;

int compute = x1*y2 + x3*y1 + x2*y3 - x3*y2 - x2*y1 - x1*y3;

if(compute > max)

{

max = compute;

index = i;

}

}

}

if(index!=-1) //取到array[index]（即最高点），这个点与array[final]、array[first]构成的三角形面积最大

{

Add(array,result,index);

DealWithLeft(first,index,array,result);

DealWithLeft(index,final,array,result);

}

}