分治思想的几个算法：二分检索、快排、归并排序

/*分治思想的各种算法*/
#include <stdlib.h>
#include <stdio.h>

/*二分检索算法*/
int BinarySearch(int a[],int n,int e)
{
int index;
int low=0,high=n-1, mid;

while(low <= high)
{
mid = (low + high) / 2;
if(e == a[mid])return mid;
else if(e > a[mid])low = mid + 1;
else high = mid - 1;
}

if(low >= high)return -1;
}

/*归并排序算法*/
void MergeSort(int a[],int low,int high)
{
int mid;
int temp[100],i,j,k;

if(high == low)return;

/*先细分排序*/
mid = (low + high)/2;
MergeSort(a,low,mid);
MergeSort(a,mid+1,high);

/*再归并*/
i=low,j=mid+1,k=0;
while(i<=mid && j<=high)
{
if(a[i] < a[j])temp[k++] = a[i++];
else temp[k++] = a[j++];
}
for(;i<=mid;)temp[k++] = a[i++];
for(;j<=high;)temp[k++] = a[j++];

for(i=low,j=0;i<=high;)a[i++] = temp[j++];
}
/*快排,快速划分*/
int Partion(int a[],int low,int high)
{
int v = a[low];

if(low >= high)return;

while(low < high)
{
while(a[high] >= v && high > low)high--;
a[low] = a[high];

while(a[low] <= v && high > low)low++;
a[high] = a[low];
}
a[low] = v;

return low;
}
void QuickSort(int a[],int low,int high)
{
int index;
if(low >= high)return;
index = Partion(a,low,high);
QuickSort(a,low,index-1);
QuickSort(a,index+1,high);
}
/*打印出来*/
void print(int a[],int n)
{
int i = 0;
while(i < n)printf("%d\t",a[i++]);
printf("\n");
}
int main(int argc, char *argv[])
{
//int a[] = {0,1,2,3,4,5,6,7,8,9};
int a[] = {2,4,6,8,9,7,5,3,1,0};
int n = 10;

QuickSort(a,0,9);
print(a,10);
printf("Position : %d\n",BinarySearch(a,n,4));

return 0;
}