No.27 Remove Element

Given an array and a value, remove all instances of that value in place and return the new length.

The order of elements can be changed. It doesn't matter what you leave beyond the new length.

移除数组中所有的给定数字
要求：原地移除，不能使用额外空间；返回新数组的长度;可以改变原始顺序

典型的两指针

 1 #include "stdafx.h"
 2 #include <map>
 3 #include <vector>
 4 #include <iostream>
 5 using namespace std;
 6 
 7 class Solution
 8 {
 9 public:
10     int removeElement(vector<int> &nums, int val)
11     {//移除数组中所有的给定数字
12      //要求：原地移除，不能使用额外空间；返回新数组的长度;可以改变原始顺序
13         int size = nums.size();
14         int count = 0;//计数当前val出现的次数
15 
16         for(int i=0; i<size; i++)
17         {
18             if(nums[i] == val)
19                 count++;
20             else
21             {
22                 if(count != 0)
23                     nums[i-count] = nums[i];
24             }
25         }
26         nums.erase(nums.begin()+size-count,nums.end());
27         return size-count;
28     }
29 };
30 
31 int main()
32 {
33     Solution sol;
34     int data[] = {1,2,2,3,3,2,1,7,9,10};
35     vector<int> test(data,data+sizeof(data)/sizeof(int));
36     for(const auto &i : test)
37         cout << i << " ";
38     cout << endl;
39     cout<< boolalpha << sol.removeElement(test,2)<<endl;
40         for(const auto &i : test)
41         cout << i << " ";
42     cout << endl;    
43 }