[LeetCode] Search a 2D Matrix

public class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        int low=0, high=matrix.length-1;
        while (low<high) {
            int mid = (low+high)/2+1;
            if (matrix[mid][0] > target) high = mid-1;
            else low = mid;
        }
        
        int index1 = low;
        
        low = 0;
        high = matrix[0].length-1;
        while (low<high) {
            int mid = (low+high)/2+1;
            if (matrix[index1][mid] > target) high = mid-1;
            else low = mid;
        }
        
        return matrix[index1][low] == target;
    }
}