查找最大子数组

最新推荐文章于 2021-01-25 15:23:32 发布

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[size=large][color=blue][b]查找一个数组的最大子数组[/b][/color][/size]
[size=medium]如：
a=[13,-3,-25,20,-3,-16,-23,18,20,-7,12,-5,-22,15,-4,7]
最大子数组为[7,10],最大值为43[/size]
python代码如下



def corss_mid(a,low,mid,high):
    left_sum=-1000;
    sum=0;
    max_left=mid
    for i in range(mid,low,-1):
        sum+=a[i]
        if sum>left_sum:
            left_sum=sum
            max_left=i

    right_sum=-1000
    sum=0
    max_right=mid
    for j in range(mid+1,high,1):
        sum+=a[j]
        if sum>right_sum:
            right_sum=sum
            max_right=j
    return (max_left,max_right,left_sum+right_sum)

def find_max(a,low,high):
    if high==low:
        return (low,high,a[low])
    else:
         mid=(low+high)/2

         (left_low,left_high,left_sum)=find_max(a,low,mid)
         (right_low,right_high,right_sum)=find_max(a,mid+1,high)
         (crose_low,cross_high,cross_sum)=corss_mid(a, low, mid, high)

         if left_sum>=right_sum and left_sum>=cross_sum:
             return (left_low,left_high,left_sum)
         elif right_sum>=left_sum and right_sum>cross_sum:
             return (right_low,right_high,right_sum)
         else:
             return (crose_low,cross_high,cross_sum)


a=[13,-3,-25,20,-3,-16,-23,18,20,-7,12,-5,-22,15,-4,7]
print find_max(a,0,15)