为什么只循环了一次?

Question

#include"stdio.h"#include"string.h"#include"conio.h"#include"windows.h"#define  NUM  8void invert ( int *,int );  //函数说明语句void priout ( int *,int );  //函数说明语句main(){ int a[NUM] = {10,20,30,40,50,60,70,80}; printf("输出原始数据: \n"); priout ( a,NUM ); invert ( a,NUM ); printf("输出颠倒后的数据: \n"); priout ( a,NUM ); return 0;}void priout ( int s[],int n ){ int i; for ( i = 0; i < n; i ++ ) {  printf("%4d",s[i]); } printf("\n");}void invert ( int *a,int n ){ int i,j,t; i = 0;     //i是最前元素的下标 j = n - 1;    //j是最后元素的下标  while ( i <= j )  //当i大于或等于j时,对调完成 {  t = a[i];   //下标为i和j的两个元素中的值对调  a[i] = a[j];  a[j] = t;  a ++;    //i向后移一个位置  j --;    //j向前移一个位置 } }请大神解答!