码迷,mamicode.com
首页 > 编程语言 > 详细

【算法设计-分治】最大子数组问题

时间:2015-04-24 14:19:44      阅读:201      评论:0      收藏:0      [点我收藏+]

标签:算法   分治   

1.问题描述

算法导论上38页,最大子数组给出一组数组来,然后求出使得从i到j的数组值的和最大的边界i与j。如果不用分治的方法的话,需要通过暴力方法来寻找n(n-1)/2种。

方法:

技术分享

技术分享

2代码:


#include<iostream>
using namespace std;
typedef struct maximum
{
int left;
int right;
int sum;
}Maximum;
Maximum* FIND_MAX_CROOSING_SUBARRAY(int *A,int low,int mid,int high);
Maximum* FIND_MAXIMUM_SUBARRAY(int *A,int low,int high);
Maximum* FIND_MAX_CROOSING_SUBARRAY(int *A,int low,int mid,int high)
{
Maximum *mymaximum=new Maximum;
int left_sum=INT_MIN;
int right_sum=INT_MIN;
int i,j;
int sum=0;
for(i=mid;i>=low;i--)
{
sum=sum+A[i];
if(sum>left_sum)
{
 
    left_sum=sum;
mymaximum->left=i;
}
}
sum=0;
    for(j=mid+1;j<=high;j++)
{
sum=sum+A[j];
if(sum>right_sum)
{
    right_sum=sum;
mymaximum->right=j;
}
}
mymaximum->sum=left_sum+right_sum;
return mymaximum;
}
Maximum* FIND_MAXIMUM_SUBARRAY(int *A,int low,int high)
{
int mid;
Maximum *leftmymaximum=new Maximum;;
Maximum *rightmymaximum=new Maximum;
Maximum *mycross=new Maximum;


if(low!=high)
{
 mid=(low+high)/2;
 leftmymaximum=FIND_MAXIMUM_SUBARRAY(A,low,mid);
 rightmymaximum=FIND_MAXIMUM_SUBARRAY(A,mid+1,high);
 mycross=FIND_MAX_CROOSING_SUBARRAY(A,low,mid,high);
}
if(((leftmymaximum->sum)>=(rightmymaximum->sum))&&((leftmymaximum->sum)>=(mycross->sum)))
return leftmymaximum;
else if((rightmymaximum->sum)>=(leftmymaximum->sum)&&(rightmymaximum->sum)>=(mycross->sum))
return rightmymaximum;
else
return mycross;
}
int main(void)
{
int totalnum;
int i=1;
int t;
int *A=new int;
Maximum *mymaximum=new Maximum;
  printf("您的数组一共有多少个数字?\n");
  scanf("%d",&totalnum);
  printf("请输入您要输入的数组?以-123\n");
  for(i=1;i<=totalnum;i++)
 scanf("%d",&A[i]);
  mymaximum=FIND_MAXIMUM_SUBARRAY(A,1,totalnum);
  printf("最大子数组的左边界是%d\n",mymaximum->left);
  printf("最大子数组的右边界是%d\n",mymaximum->right);
  printf("最大子数组的和是%d\n",mymaximum->sum);
  return 0;
}

结果:

技术分享

【算法设计-分治】最大子数组问题

标签:算法   分治   

原文地址:http://blog.csdn.net/wodeai1625/article/details/45244731

(0)
(0)
   
举报
评论 一句话评论(0
登录后才能评论!
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码!