简单的冒泡法排序，不知道为啥在vs2017上编译出错 显示 Run-Time Check Failure #2 - Stack around the variable a was corrupted

多谢指教！


#include<stdio.h>

int main()
{
    int i,j,t=0;
    int a[] = { 1,3,6,2,5 };
    for (i = 1;i <= 4;i++) {
        for (j = 1;j <= 5 - i;j++)
            if (a[j] > a[j+1]) {
                t = a[j+1];
                a[j+1] = a[j];
                a[j] = t;
            }
    }
    printf("\n");
    for (i = 0;i < 5;i++) {
        printf("%d", a[i]);
    }
    return 0;
}

大佬能否帮忙细讲一下啥是越界...感觉不是很懂。因为我先定义数组再定义i这些变量，编译还是出错。