复习版

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

#define not !
#define and &&
#define or ||

#define ri register int
#define rep(inc, frm, to) for (ri inc = frm; inc < (to); ++inc)
#define rep2(inc, frm, to) for (ri inc = frm; inc > (to); --inc)

typedef long long int ll;
#define r() fast_read()

bool is_digit(const char c) {
  return c >= 48 and c <= 57;
}

ll fast_read(void) {
  ll n = 0, sign = 1;
  char c = getchar();
  while (not is_digit(c)) {
    if (c == '-') sign = ~0;
    c = getchar();
  }
  while (is_digit(c)) {
    n = (n << 1) + (n << 3) + (c ^ 48);
    c = getchar();
  }
  return sign * n;
}

int cnts[1 << 24];

signed main(int argc, char const *argv[]) {
  int n = r(), m = r(), color;
  rep(y, 0, m) rep(x, 0, n) {
    color = r();
    if (++cnts[color] > (n * m) >> 1) {
      printf("%d\n", color);
      return 0;
    }
  }
  return ~~(0 ^ 0);
}

HashTable Again!

#include <iostream>
#include <unordered_map>

using namespace std;
int m, n, id;

unordered_map<int, int> freq;

int main(int argc, char** argv) {
  cin >> m >> n;
  for (int y = 0; y < m; ++y)
    for (int x = 0; x < n; ++x) {
      cin >> id;
      if (++freq[id] > (m * n) >> 1)
        return printf("%d\n", id), 0;
    }

  return 0;
}