【数组】连续子数组的最大和

2019-10-10  本文已影响0人  一个想当大佬的菜鸡
# -*- coding:utf-8 -*-
class Solution:
    def FindGreatestSumOfSubArray(self, array):
        # write code here
        m = len(array)
        dp = [0 for _ in range(m)]
        dp[0] = array[0]
        res = float("-inf")
        for i in range(1, m):
            dp[i] = max(0, dp[i-1]) + array[i]
            res = max(dp[i], res)
        return res

扩展成2维的

class Solution:
    def FindGreatestSumOfSubArray(self, array):
        # write code here
        m = len(array)
        dp = [0 for _ in range(m)]
        dp[0] = array[0]
        res = float("-inf")
        for i in range(1, m):
            dp[i] = max(0, dp[i-1]) + array[i]
            res = max(dp[i], res)
        return res
    def FindGreatestSumOfSubArray2(self, array):
        m, n = len(array), len(array[0])
        res = float("-inf")
        temp = [0 for _ in range(n)]
        for i in range(m):
            for j in range(i, m):    #确定上下边界,找最大子矩阵,转化成1维的问题
                for k in range(n):
                    if i == j:
                        temp[k] = 0
                    temp[k] += array[j][k]
                print(i, j, temp)
                res = max(res, self.FindGreatestSumOfSubArray(temp))
        return res

if __name__ == "__main__":
    A = [[1, 5, -3, 6, -7], [3, 5, -9, -4, 6], [-8, 4, 0, 12, -3], [3, -1, 5, -5, 8]]
    s = Solution()
    print(s.FindGreatestSumOfSubArray2(A))
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