这是什么意思啊 int left = i; while (left)

#include <algorithm>
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <cmath>
using namespace std;
int f[10000][10];
int main()
{
memset(f, 0, sizeof(f));
for (int i = 1 ; i < 10000 ; ++ i) {
for (int j = 0 ; j < 10 ; ++ j)
f[i][j] = f[i-1][j];
int left = i;
while (left) {
f[i][left%10] ++;
left /= 10;
}
}
int t,n;
while (~scanf("%d",&t))
while (t --) {
scanf("%d",&n);
for (int i = 0 ; i < 9 ; ++ i)
printf("%d ",f[n][i]);
printf("%d\n",f[n][9]);
}
return 0;
}