378. Kth Smallest Element in a Sorted Matrix

public class Solution {    public boolean guess(int g,int[][] matrix, int k, int n){        int sum = 0;        for(int i = 0; i < n; i++){            int L = 0;            int R = n-1;             int ans = -1;            while(L <= R){                int mid = (L + R) / 2;                if(matrix[i][mid] < g){                    ans = mid;                    L = mid + 1;                }else{                    R = mid - 1;                }            }            sum  += (ans + 1);        }        return k > sum;            }    public int kthSmallest(int[][] matrix, int k) {        int n = matrix.length;        int L = matrix[0][0];        int R = matrix[n-1][n-1];        int ans = 0;        while(L <=  R){            int mid = (int)(((long)L + R )/2);            if(guess(mid,matrix,k,n)){                ans = mid;                L  = mid + 1;            }else{                R = mid - 1;            }        }        return ans;    }}