leetcode 363. Max Sum of Rectangle No Larger Than K

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Given a non-empty 2D matrix matrix and an integer k, find the max sum of a rectangle in the matrix such that its sum is no larger than k.

Example:

Given matrix = [
  [1,  0, 1],
  [0, -2, 3]
]
k = 2

The answer is 2. Because the sum of rectangle [[0, 1], [-2, 3]] is 2 and 2 is the max number no larger than k (k = 2).

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class Solution(object):
    def maxSubArray(self,nums,k):
        
        cumset=[]
        cumset.append(0)
        maxsum=-1<<32
        cursum=0
        for i in range(len(nums)):
            cursum+=nums[i]
            # find the lower bound of the index
            idx=bisect.bisect_left(cumset,cursum-k)
            # find max in sum[right]-sum[left]<=k
            if 0<=idx<len(cumset):
                maxsum=max(maxsum,cursum-cumset[idx])
            # using insort instead of append since bisect_left reason
            bisect.insort(cumset,cursum)
        return maxsum
    def maxSumSubmatrix(self,matrix, k):
    
        if not matrix or not matrix[0]:
            return 0
        row,col=len(matrix),len(matrix[0])
        res=-(1<<32)
        for left in range(col):
            cursums=[0 for _ in range(row)]
            right=left
            while right<col:
                for i in range(row):
                    cursums[i]+=matrix[i][right]
                curarrmax=self.maxSubArray(cursums,k)
                res=max(res,curarrmax)
                right+=1

        return res