蛇形填数问题，为什么在a[1][0]到a[0][0]之间间隔为2啊？求回答。

Question

#include<stdio.h>
#include<string.h>
//蛇形填数 
#define maxn 20
int a[maxn][maxn];
int main(){
    int n,x,y,tot = 0;
    scanf("%d",&n);
    memset(a,0,sizeof(a));
    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]){
            tot = tot + 1;
            a[x][--y] = tot;
        }
    //  printf("%d\n",tot);
        while(x-1 >= 0 && !a[x-1][y]){
            tot = tot + 1;
            a[--x][y] = tot;
        }
        //printf("%d\n",tot);
        while(y+1 < n && !a[x][y+1])
            a[x][y++] = ++tot;
    }
    for(x = 0;x < n;x++){
        for(y = 0;y < n;y++)
           printf("%3d",a[x][y]);
        printf("\n");
    }
    return 0;
} 

如上图所示，求大神解答，谢谢

Answer 1

a[x][y++] = ++tot;
->
a[x][++y] = ++tot;

// Q1065109.cpp : Defines the entry point for the console application.
//


#include<stdio.h>
#include<string.h>
//蛇形填数 
#define maxn 20
int a[maxn][maxn];
int main(){
    int n,x,y,tot = 0;
    scanf("%d",&n);
    memset(a,0,sizeof(a));
    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]){
            tot = tot + 1;
            a[x][--y] = tot;
        }
    //  printf("%d\n",tot);
        while(x-1 >= 0 && !a[x-1][y]){
            tot = tot + 1;
            a[--x][y] = tot;
        }
        //printf("%d\n",tot);
        while(y+1 < n && !a[x][y+1])
            a[x][++y] = ++tot;
    }
    for(x = 0;x < n;x++){
        for(y = 0;y < n;y++)
           printf("%3d",a[x][y]);
        printf("\n");
    }
    return 0;
} 

8
22 23 24 25 26 27 28 1
21 44 45 46 47 48 29 2
20 43 58 59 60 49 30 3
19 42 57 64 61 50 31 4
18 41 56 63 62 51 32 5
17 40 55 54 53 52 33 6
16 39 38 37 36 35 34 7
15 14 13 12 11 10 9 8
Press any key to continue . . .

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