Why did the cow cross the road?

Debugging Help
#1

Problem Info

Why did the cow cross the road?
(USACO)

My Work

#include <iostream>
#include <utility>
#include <vector>
#include <algorithm>
#include <string>
#include <cmath>

using namespace std;
using ll = long long;

/*#define f first
#define s second*/
#define FOR(i,n) for(int i=0;i<(int)(n);i++)
#define vec vector<int>
#define pb push_back
#define pi pair<int, int>
#define nl '\n'

void setIO(string name) {
  ios_base::sync_with_stdio(0); cin.tie(0);
  if(name.length()) {
		freopen((name+".in").c_str(), "r", stdin);
		freopen((name+".out").c_str(), "w", stdout);
	}
}

struct Cow {
	int s, f, r, sreach, freach;
} cows[20000];

int C, N;
int cvals[20000];
bool taken[20000];

int main() {
  setIO("helpcross");
	cin >> C >> N;
	FOR(i, C)
		cin >> cvals[i];
	FOR(i, N)
		cin >> cows[i].s >> cows[i].f;
	sort(cvals, cvals + C);
	
	FOR(i, N) {
		int *begin = lower_bound(cvals, cvals + C, cows[i].f), *end = lower_bound(cvals, cvals + C, cows[i].s);
		int amount = begin - end;
		cows[i].r = amount;
		cows[i].sreach = end - cvals;
		cows[i].freach = begin - cvals;
	}
	
	sort(cows, cows + N, [](Cow a, Cow b){
		return a.f < b.f; // sort based on ending time
	});
	int gotten = 0;
	FOR(i, N) {
		for (int j = cows[i].sreach; j < C && j < cows[i].freach; j++) {
			if (!taken[j]) {
				taken[j] = true;
				gotten++;
				break;
			}
		}
	}
	cout << gotten << nl;
}

Add explanation of code here
I take the earliest-finishing cow and match that first and then so on. I believe that I am off by one on test case 5, but I don’t know why.

What I’ve Tried

I downloaded the test data and ran it on my computer

Question

Why does this not work on test case 5 but on all other test cases it does work?

#2
  • We expect that you have already tried generating small counter-tests (as described in the module) but you haven’t found one that your program fails on. Include the generator code.

Have you tried this?