题目描述:
HZ偶尔会拿些专业问题来忽悠那些非计算机专业的同学。今天测试组开完会后,他又发话了:在古老的一维模式识别中,常常需要计算连续子向量的最大和,当向量全为正数的时候,问题很好解决。但是,如果向量中包含负数,是否应该包含某个负数,并期望旁边的正数会弥补它呢?例如:{6,-3,-2,7,-15,1,2,2},连续子向量的最大和为8(从第0个开始,到第3个为止)。给一个数组,返回它的最大连续子序列的和,你会不会被他忽悠住?(子向量的长度至少是1)
实现1――根据数据的特征:
class Solution: def FindGreatestSumOfSubArray(self, array): # write code here input_invalid = False if array is None or len(array) <= 0: input_invalid = True return 0 cursum = 0 greatsum = array[0] for i in array: if cursum < 0: cursum = i else: cursum += i if cursum > greatsum: greatsum = cursum return greatsum
实现2:―― 动态规划
def rec_DP(self, array): input_invalid = False if array is None or len(array) <= 0: input_invalid = True return 0 alist = [0]*len(array) for i in range(len(array)): if i == 0 or alist[i-1] <= 0: alist[i] = array[i] else: alist[i] = alist[i-1]+array[i] return max(alist)
测试:
s = solution() arr1 = [1, -2, 3, 10, -4, 7, 2, -5] arr2 = [-2,-8,-1,-5,-9] print(s.FindGreatestSumOfSubArray(arr1)) print(s.FindGreatestSumOfSubArray(arr2)) print(s.rec_DP(arr1)) print(s.rec_DP(arr1))
文章来源: https://blog.csdn.net/weixin_40314385/article/details/90028681