C++ 代码

class Solution {
public:
    bool findNumberIn2DArray(vector<vector<int>>& matrix, int target) {
        if (matrix.empty() || matrix[0].empty()) return false;
        int m = matrix.size(), n = matrix[0].size();
        int up = 0, down = m - 1, left = 0, right = n - 1;
        int l, r;

        while (left < right || up < down)
        {
            int new_left, new_right, new_up, new_down;

            l = left, r = right;
            while (l < r)
            {
                int mid = l + r >> 1;
                if (matrix[down][mid] >= target) r = mid;
                else l = mid + 1;
            }
            new_left = l;

            l = left, r = right;
            while (l < r)
            {
                int mid = l + r + 1 >> 1;
                if (matrix[up][mid] <= target) l = mid;
                else r = mid - 1;
            }
            new_right = l;

            l = up, r = down;
            while (l < r)
            {
                int mid = l + r + 1 >> 1;
                if (matrix[mid][new_left] <= target) l = mid;
                else r = mid - 1;
            }
            new_down = l;

            l = up, r = down;
            while (l < r)
            {
                int mid = l + r >> 1;
                if (matrix[mid][new_right] >= target) r = mid ;
                else l = mid + 1;
            }
            new_up = l;

            if (new_left == left && new_right == right && new_up == up && new_down == down)
                return true; //如果都不变的话  则是答案 返回即可
            //更新答案
            left = new_left, right = new_right;
            up = new_up, down = new_down;
        }
        return matrix[up][left] == target;
    }
};