算法入门经典P40-3-3（C表达式的简洁写法）

#include<iostream>
#define maxn 20
int a[maxn][maxn];
#include<string.h>
using namespace std;
int main(){
    int x,y,tot = 0,n;
    scanf("%d",&n);
    tot = a[x=0][y=n-1] = 1;
    while(tot<n*n){
        while(x+1<n    &&!a[x+1][y])     a[++x][y] = ++tot;
        while(y-1>=0&&!a[x][y-1])     a[x][--y] = ++tot;
        while(x-1>=0&&!a[x-1][y])    a[--x][y] = ++tot;
        while(y+1<n    &&!a[x][y+1])    a[x][++y] = ++tot;
    }
    for(int i=0;i<n;i++){
        for(int j=0;j<n;j++){
            printf("%3d",a[i][j]);
        }
        printf("\n");
    }
    return 0;
}