这道题可以直接暴力法解出答案，但是如果对时间有要求，可以对每一行使用二分进行查找。

public boolean searchMatrix(int[][] matrix, int target) {
        for (int[] row : matrix) {
            int index = search(row, target);
            if (index >= 0) {
                return true;
            }
        }
        return false;
    }

    public int search(int[] nums, int target) {
        int low = 0, high = nums.length - 1;
        while (low <= high) {
            int mid = (high - low) / 2 + low;
            int num = nums[mid];
            if (num == target) {
                return mid;
            } else if (num > target) {
                high = mid - 1;
            } else {
                low = mid + 1;
            }
        }
        return -1;
    }