max-sum-of-sub-matrix-no-larger-than-k

根据上一篇文章提到的参考文档：

https://leetcode.com/discuss/109749/accepted-c-codes-with-explanation-and-references

我实现的解法，用了一个sum_max，不再另设res。

class Solution {
public:
    int maxSumSubmatrix(vector<vector<int>>& matrix, int K) {
        int sum_max = INT_MIN;
        int rlen = matrix.size();
        int clen = matrix[0].size();
        
        for (int i=0; i<clen; i++) {
            vector<int> tmp_vec(rlen, 0);
            for (int j=i; j<clen; j++) {
                for (int k=0; k<rlen; k++) {
                    tmp_vec[k] += matrix[k][j];
                }
                
                set<int> cur_max_set;
                int cur_max = 0;
                for (int k=0; k<rlen; k++) {
                    cur_max += tmp_vec[k];
                    if (cur_max <= K) {
                        sum_max = max(sum_max, cur_max);
                    }
                    set<int>::iterator iter = cur_max_set.lower_bound(cur_max - K);
                    if (iter != cur_max_set.end()) {
                        sum_max = max(sum_max, cur_max-*iter);
                    }
                    cur_max_set.insert(cur_max);
                }
            }
        }
        return sum_max;
    }
};

27 / 27 test cases passed.	Status:  Accepted
Runtime: 1016 ms