LeetCode/cpp/count-negative-numbers-in-a-sorted-matrix.cpp

#include <algorithm>
#include <cassert>
#include <vector>

class Solution {
  public:
    int countNegatives(const std::vector<std::vector<int>> &grid) {
        auto last = 0;

        auto negatives = 0;
        for (const auto &row : grid) {
            auto first_positive =
                std::lower_bound(row.crbegin() + last, row.crend(), 0);
            auto i = first_positive - row.crbegin();

            negatives += i;
            last = i;
        }
        return negatives;
    }
};

int main() {
    Solution s;

    assert((s.countNegatives(std::vector{
                std::vector{4, 3, 2, -1}, std::vector{3, 2, 1, -1},
                std::vector{1, 1, -1, -2}, std::vector{-1, -1, -2, -3}}) == 8));
    assert((s.countNegatives(
                std::vector{std::vector{3, 2}, std::vector{1, 0}}) == 0));
    return 0;
}