# 1089.Duplicate Zeros

**1089.Duplicate Zeros**

难度:Easy

> 给你一个长度固定的整数数组 arr，请你将该数组中出现的每个零都复写一遍，并将其余的元素向右平移。

注意：请不要在超过该数组长度的位置写入元素。

要求：请对输入的数组 就地 进行上述修改，不要从函数返回任何东西。

```
示例 1：

输入：[1,0,2,3,0,4,5,0]
输出：null
解释：调用函数后，输入的数组将被修改为：[1,0,0,2,3,0,0,4]
示例 2：

输入：[1,2,3]
输出：null
解释：调用函数后，输入的数组将被修改为：[1,2,3]
 

提示：

1 <= arr.length <= 10000
0 <= arr[i] <= 9
```

使用一个堆栈来保留前N项，最后复制到数组中即可。注意堆栈的大小。

```
class Solution {
public:
    void duplicateZeros(vector<int>& arr) {
        if(arr.size()==1) return ;
        stack<int> num;
        for(auto a: arr)
        {
            num.push(a);
            if(!a) num.push(a);
            
            if(num.size()>=arr.size()) break;
        }
        if(num.size()>arr.size()) num.pop();
        int start=num.size()-1;
     //   cout<<start<<endl;
        while(!num.empty())
        {
            arr[start--]=num.top();
            num.pop();
        }
        
    }
};
```

> 执行用时 :28ms, 在所有 C++ 提交中击败了91.37%的用户\
> 内存消耗 :9.4MB, 在所有 C++ 提交中击败了100%的用户


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