分治求两相同大小有序序列中位数

$TestData$

输入	值
数组大小	3
A组元素	5 15 18
B组元素	3 14 21

此代码是从文件读取数据

#include <iostream>
#include <fstream>
#include <sstream>
using namespace std;

int searchMid(int A[], int B[], int n){
    int start1 = 0, end1 = n - 1;
    int start2 = 0, end2 = n - 1;
    int mid1, mid2;
    while (start1 < end1 && start2 < end2) {
        mid1 = (start1 + end1) / 2;
        mid2 = (start2 + end2) / 2;
        if (A[mid1] == B[mid2]) {
            return A[mid1];
        }
        if (A[mid1] < B[mid2]) {
            if ((start1 + end1)%2 == 0) {
                start1 = mid1;
            }
            else{
                start1 = mid1 + 1;
            }
            end2 = mid2;
        }
        else{
            if ((start2 + end2) % 2 == 0) {
                start2 = mid2;
            }
            else{
                start2 = mid2 + 1;
            }
            end1 = mid1;
        }
    }
    if (A[start1] < B[start2]) {
        return A[start2];
    }
    else{
        return B[start1];
    }
}

int main(int argc, const char * argv[]) {
    ifstream in("/median_num/input.txt");
    
    string s;
    istringstream first;
    int n;
    if (in) {
        getline(in, s);
        first.str(s);
        first>>n;
    }
    int A[n];
    int B[n];
    string line;
    istringstream instr;
    for (int i = 0;  i < 2; ++i) {
        getline(in, line);
        instr.str(line);
        for (int j = 0; j < n; ++j) {
            if (i == 0){
                instr>>A[j];
            }
            else{
                instr>>B[j];
            }
        }
    }
    int re;
    re = searchMid(A, B, n);
    cout<<re<<endl;
    return 0;
}