数列最大连续子数组和

一、分治法：
算法复杂度：O(nlgn)

#include <iostream>#include <vector>using namespace std;int A[]={-2,1,-3,4,-1,2,1,-5,4};int CrossSubArray(int A[],int low,int high,int mid){    int left_max=0x80000000;    int right_max=0x80000000;    int sum=0;    for(int i=mid;i>=low;--i)    {        sum+=A[i];        if(sum>left_max) left_max=sum;    }    sum=0;    for(int i=mid+1;i<=high;++i)    {        sum+=A[i];        if(sum>right_max) right_max=sum;    }    return left_max+right_max;}int MaxSubArray(int A[],int low,int high){    if(low==high) return A[low];    int mid=(low+high)/2,L,R,Cr;    L=MaxSubArray(A,low,mid);    R=MaxSubArray(A,mid+1,high);    Cr=CrossSubArray(A,low,high,mid);    return max(max(L,R),Cr);}int main(){    int n=sizeof(A)/sizeof(int);    cout<<MaxSubArray(A,0,n-1);    return 0;}

二、Dp法：
算法复杂度：O(n)

#include <iostream>#include <vector>#include <algorithm>using namespace std;vector<int> v={-1,2,-5,3,5,9,-1,22,8};int MaxSubArray(vector<int> v){    int maxsum=v[0],sum=0;    for(auto x:v)    {        sum+=x;        maxsum=max(maxsum,sum);        sum=max(sum,0);    }    return maxsum;}int main(){    cout<<MaxSubArray(v);    return 0;}