MaxSubArray 最大子数列和

 public int maxSubArray(int[] A) {
            int newsum=A[0];
            int max=A[0];
            for(int i=1;i<A.length;i++){
                newsum=Math.max(newsum+A[i],A[i]);
                max= Math.max(max, newsum);
            }
            return max;
         }

 int maxSubArray(int *a, const int length)
 {
     int maxSumSubArray = ;
     int sum_i = ;
     for(int i=; i <length; i++)
     {
        sum_i = sum_i + a[i];
        if(sum_i < ) sum_i = ;
         else
         {
             if(sum_i > maxSumSubArray) maxSumSubArray = sum_i;
         }
     } 

     //若是数组中的元素均为负值
     if(sum_i==)
     {
         for(int i=; i < length; i++)
         {
             if(a[i] > maxSumSubArray) maxSumSubArray = a[i];
         }
     }
     return maxSumSubArray;
 } 

还有一种是分治算法 自己写的 复杂度O（nlogn）

 #include<iostream>
 using namespace std;
 int MaxSubArray(int *A,int low,int high){
     if(low==high) return A[low];
     int mid=(low+high)/;
     int maxl=MaxSubArray(A,low,mid);
     int maxr=MaxSubArray(A,mid+,high);
     int maxleft=A[mid],maxright=A[mid+],maxsum;
     maxsum=A[mid];
     if(mid->=low)
     for(int i=mid-;i>=low;i--){
         maxsum=maxsum+A[i];
         maxleft=max(maxsum,maxleft);
     }
     maxsum=A[mid+];
     if(mid+<=high)
     for(int i=mid+;i<=high;i++){
         maxsum=maxsum+A[i];
         maxright=max(maxsum,maxright);
     }
     int cross=maxleft+maxright;
     return max(cross,max(maxl,maxr));

 }
 int main(){
     int a[]={,-,,,-,};
     cout<<MaxSubArray(a,,)<<endl;
     return ;
 }