oj-1-蛇形填数

#include<stdio.h>#include<string.h>#define maxn 20int a[maxn][maxn];int main(){    int n,x,y,tot = 0;     scanf("%d", &n);    memset(a, 0, sizeof(a));  //初始化数组    tot = a[x=0][y=n-1] = 1;    while(tot < n*n) //实际上tot的最大值为n^2,对应++tot     {        while(x+1<n && !a[x+1][y])  a[++x][y] = ++tot;//先改变再判断是否移动         while(y-1>=0 && !a[x][y-1])  a[x][--y] = ++tot;//此处可以将"<n"理解为"<=n-1",         while(x-1>=0 && !a[x-1][y])  a[--x][y] = ++tot;//n-1是二维数组的边界         while(y+1<n && !a[x][y+1])   a[x][++y] = ++tot;//对应填字顺序     }    for(x=0; x<n; x++)    {        for(y=0; y<n; y++) printf("%3d", a[x][y]); //%3d 为了空格         printf("\n");    }    return 0;}