【經典算法】:蛇形填數

題目地址:http://acm.nyist.net/JudgeOnline/problem.php?pid=33

while( count < N*N ){
        while(x+1<n && !a[x+1][y]) a[++x][y]=++count;//右下
        while(y-1>=0 &&!a[x][y-1]) a[x][--y]=++count;//向左
        while(x-1>=0 &&!a[x-1][y]) a[--x][y]=++count;//左上
        while(y+1<n &&!a[x][y+1])  a[x][++y]=++count;//向右
    }