复习总结提高版

#include <stdio.h>
#include <stdlib.h>
#include <math.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)

#define MAX_N 10010

int n, M, N, nums[MAX_N];

int cmp(const void* e1, const void* e2) {
  return *(int*) e2 - *(int*) e1;
}

void print_arr(int arr[], const size_t sz) {
  rep(i, 0, sz) printf("%d%c", *(arr + i), i == sz - 1 ? 10 : 32);
}

signed main(int argc, char const *argv[]) {
  scanf("%d", &n);
  rep(i, 0, n) scanf("%d", nums + i);
  qsort(nums, n, sizeof(int), cmp);
  for (ri i = sqrt(n); i; --i)
    if (not(n % i)) {
      M = n / i, N = i;
      break;
    }

  int matrix[M][N];

  int top = 0, bottom = M - 1, left = 0, right = N - 1, dir = 0, cnt = 0;
  while (top <= bottom and left <= right) {
    switch (dir) {
      case 0: // 由左至右
        for (ri x = left; x <= right; ++x)
          *(*(matrix + top) + x) = *(nums + cnt++);
        ++top;
        break;
      case 1:
        for (ri y = top; y <= bottom; ++y)
          *(*(matrix + y) + right) = *(nums + cnt++);
        --right;
        break;
      case 2:
        for (ri x = right; x >= left; --x)
           *(*(matrix + bottom) + x) = *(nums + cnt++);
         --bottom;
        break;
      case 3:
        for (ri y = bottom; y >= top; --y)
           *(*(matrix + y) + left) = *(nums + cnt++);
         ++left;
        break;
      default:
        puts("something is wrong!!!");
        break;
    }
    dir = (dir + 1) % 4;
  }

  rep(y, 0, M) rep(x, 0, N)
    printf("%d%c", *(*(matrix + y) + x), x == N - 1 ? 10 : 32);

  return ~~(0 ^ 0);
}

模拟！

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

using namespace std;
int n, M, N;

int main(void) {
  cin >> n;
  vector<int> nums(n);
  for (int i = 0; i < n; ++i) cin >> nums[i];
  sort(rbegin(nums), rend(nums));

  for (int i = sqrt(n); i >= 1; --i) { // 试除法
    if (!(n % i)) {
      M = n / i;
      N = i;
      break;
    }
  }

  int idx  = 0, dir    = 0, 
      left = 0, right  = N - 1,
      top  = 0, bottom = M - 1;

  vector<vector<int>> matrix(M, vector<int>(N));

  while (left <= right and top <= bottom) {
    switch (dir) {
      case 0:
        for (int x = left; x <= right; ++x)
          matrix[top][x] = nums[idx++];
        ++top;
        break;
      case 1:
        for (int y = top; y <= bottom; ++y)
          matrix[y][right] = nums[idx++];
        --right;
        break;
      case 2:
        for (int x = right; x >= left; --x)
          matrix[bottom][x] = nums[idx++];
        --bottom;
        break;
      case 3:
        for (int y = bottom; y >= top; --y)
          matrix[y][left] = nums[idx++];
        ++left;
        break;
    }
    dir = (dir + 1) % 4;
  }

  for (const auto& r : matrix) {
    for (int i = 0; i < r.size(); ++i) {
      printf("%d", r[i]);
      if (i < r.size() - 1) putchar(' ');
    }
    putchar('\n');
  }
}