分治法求最大子数组 c语言实…

#define TYPE_MIN INT_MIN
typedef int type_i;
typedef struct return_t
{
int left;
int right;
type_i sum;
} return_type;
return_type find_max_crossing_subarray(type_i *A,int low,int mid,int high)
{
type_i left_sum=TYPE_MIN;
type_i sum=0;
int i;
int max_left;
for(i=mid;i>=low;i--)
{
sum+=A[i];
if(sum>left_sum)
{
left_sum=sum;
max_left=i;
}
}
type_i right_sum=TYPE_MIN;
sum=0;
int max_right;
for(i=mid+1;i<=high;i++)
{
sum+=A[i];
if(sum>=right_sum)
{
right_sum=sum;
max_right=i;
}
}
return_type r={max_left,max_right,left_sum+right_sum};
return r;
}
return_type find_maximum_subarray(type_i *A,int low,int high)
{
if(high==low)
{
return_type r={low,high,A[low]};
return r;
}
int mid=(low+high)/2;
return_type left=find_maximum_subarray(A,low,mid);
return_type right=find_maximum_subarray(A,mid+1,high);
return_type cross=find_max_crossing_subarray(A,low,mid,high);
if((left.sum>right.sum)&&(left.sum>cross.sum))
return left;
else if((right.sum>cross.sum)&&(right.sum>left.sum))
return right;
else
return cross;
}
int main()
{
int A[10]={1,2,-5,6,20,-6,2,7,10,-5};
return_type r=find_maximum_subarray(A,0,9);
printf("%d %d %d\n",r.left,r.right,r.sum);
return 0;
}