Finally One Correct in One Go!!

Really good question about binary search.

My code working on my computer but showing wrong answer in SPOJ

#include<bits/stdc++.h>
using namespace std;
int barn, cow, temp;
vector<int> pos;

bool place_them(int mid)
{
int count=1, start=pos[0];
for(int i=0; i<barn; i++)
{
if(pos[i]-start >= mid)
{
count++;
start = pos[i];
}
if(count==cow) return 1;
}
return 0;
}

int binary(int lo, int hi)
{
int mid;
while(hi-lo>1)
{
mid = lo + (hi-lo)/2;
if(place_them(mid)) lo = mid;
else hi = mid;
}
return mid;
}

int main()
{
int t;
cin >> t;
while(t--)
{
cin >> barn >> cow;
pos.clear();

for(int i=0; i<barn; i++)
{
cin >> temp;
pos.push_back(temp);
}
sort(pos.begin(), pos.end());
int lo, hi;
lo = 0;
hi = pos[barn-1] - pos[0] + 1;
temp = binary(lo, hi);
cout << temp << endl;
}
return 0;
}

nyc qs on binary search! must do!

can someonne highlight my error , it's a wrong answer while the output is 3
#include <iostream>
#include<vector>
#include<algorithm>

using namespace std;

int check(int i, vector<int> vec,int c) {
int count = 1;
int pos = 0;
int last = 0;
int maxDistance = vec.back() - vec.front();
while (pos < (vec.size())) {
if (vec[pos] - vec[last] >= i) {
count++;
maxDistance = min(maxDistance, vec[pos] - vec[last]);
last = pos;
}
pos++;
if (count == c)
return maxDistance;
}
return 0;
}

int main() {
int t;
cin >> t;
for (int i = 0; i < t; i++) {
int pos, c;
cin >> pos >> c;
vector<int> vec;
for (int j = 0; j < pos; j++) {
int p;
cin >> p;
vec.push_back(p);
}
sort(vec.begin(), vec.end());
int start = vec[0];
int end = vec.back();
int score = 0;
while (start < end) {
int mid = start + (end - start) / 2;
score = check(mid, vec, c);
if (score>0) {
start = mid + 1;
}
else {
end = mid -1;
}
}
cout << score << endl;
}
}