这里是大样例没过，但是放到自测里就能过了，然后自己编译样例也是对的
好神奇。。。
代码：
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <climits>
using namespace std;
int main(void) {
int m, n;
cin >> m >> n;
cin.ignore();
vector<vector<int>> pre(n);
for (int i = 0; i < n; ++i) {
string l;
getline(cin, l);
vector<int> p;
for (char c : l) {
p.push_back(c - '0');
}
pre[i] = p;
}
vector<bool> e(m + 1, false);
vector<int> cpos(n, 0);
while (true) {
vector<int> v(m + 1, 0);
int r = 0;
for (int i = 0; i < n; ++i) {
int pos = cpos[i];
while (pos < pre[i].size()) {
int b = pre[i][pos];
if (b == 0) break;
if (!e[b]) {
v[b]++;
break;
}
pos++;
}
cpos[i] = pos;
}
for (int i = 1; i <= m; ++i) {
if (!e[i]) {
r++;
}
}
if (r == 1) {
for (int i = 1; i <= m; ++i) {
if (!e[i]) {
cout << i << endl;
return 0;
}
}
}
int minv = INT_MAX;
for (int i = 1; i <= m; ++i) {
if (!e[i] && v[i] < minv) {
minv = v[i];
}
}
bool as = true;
int fnz = -1;
for (int i = 1; i <= m; ++i) {
if (!e[i]) {
if (fnz == -1) {
fnz = v[i];
} else if (v[i] != fnz) {
as = false;
break;
}
}
}
if (as && fnz > 0) {
cout << -fnz << endl;
return 0;
}
bool eany = false;
for (int i = 1; i <= m; ++i) {
if (!e[i] && v[i] == minv) {
e[i] = true;
eany = true;
}
}
if (!eany) {
cout << -minv << endl;
return 0;
}
}
return 0;
}