PAT A1105 . Spiral Matrix (25)

This time your job is to fill a sequence of N positive integers into a spiral matrix in non-increasing order. A spiral matrix is filled in from the first element at the upper-left corner, then move in a clockwise spiral. The matrix has m rows and n columns, where m and n satisfy the following: m*n must be equal to N; m>=n; and m-n is the minimum of all the possible values.

Input Specification:

Each input file contains one test case. For each case, the first line gives a positive integer N. Then the next line contains N positive integers to be filled into the spiral matrix. All the numbers are no more than 104. The numbers in a line are separated by spaces.

Output Specification:

For each test case, output the resulting matrix in m lines, each contains n numbers. There must be exactly 1 space between two adjacent numbers, and no extra space at the end of each line.

Sample Input:
12
37 76 20 98 76 42 53 95 60 81 58 93
Sample Output:
98 95 93
42 37 81
53 20 76
58 60 76

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#include <stdio.h>
#include <iostream>
#include <algorithm>
using namespace std;
const int INF = 1000000000;
const int maxv = 210;
int N, m, n;
int arr[10010] = {0};

bool cmp(int a, int b){
return a > b;
}
int main(){
//freopen("in.txt", "r", stdin);
scanf("%d", &N);
for(int i = 0; i < N; i++){
scanf("%d", &arr[i]);
}
int a, b, minDiff = INF;
for(a = N; a > 0 ;a--){
if(N % a == 0){//可以整除
b = N / a;
if(b > a) break;
if(a - b < minDiff && a >= b){
minDiff = a - b;
m = a;
n = b;
}
}
}
sort(arr,arr+ N,cmp);
int** matrix = new int*[m];
for(int i = 0; i < m ;i++){
matrix[i] = new int[n];
}
for(int i = 0;i < m; i++){
for(int j = 0;j < n;j++){
matrix[i][j] = 0;
}
}
int i = 0, x = 0, y = 0;
while (i < N)
{
while (y < n&&!matrix[x][y])
matrix[x][y++] = arr[i++];
y--;
x++;
while (x < m && !matrix[x][y])
matrix[x++][y] = arr[i++];
x--;
y--;
while (y >= 0 && !matrix[x][y])
matrix[x][y--] = arr[i++];
y++;
x--;
while (x >= 0 && !matrix[x][y])
matrix[x--][y] = arr[i++];
x++;
y++;
}
for(int i = 0;i < m; i++){
for(int j = 0;j < n;j++){
if(matrix[i][j]){
printf("%d", matrix[i][j]);
if(j < n - 1) printf(" ");
}
}
printf("\n");
}
return 0;
}