27. Remove Element

题目

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

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

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

Example:

Given nums = [3,2,2,3], val = 3,

Your function should return length = 2, with the first two elements of nums being 2.

解析

class Solution_27 {
public:

    // 直接查看cnt长度的元素值；若是str,最后加上‘\0’
    int removeElement(vector<int>& nums, int val) {
        int cnt = 0;
        for (int i = 0; i < nums.size();i++)
        {
            if (nums[i]!=val)
            {
                nums[cnt++] = nums[i];
            }
        }
        
        return cnt;
    }


//测试用例: 牛客网上有顺序要求
//  [1, 2, 3, 4], 1
//
//  对应输出应该为 :
//
//          [4, 2, 3]
//
//你的输出为 :
//
//  [2, 3, 4]
    int removeElement(int A[], int n, int elem) {
    
        int i = 0;
        for ( i= 0; i < n; i++)
        {
            if (A[i] == elem)
            {
                while (i<n&&A[--n] == elem);
                A[i] = A[n];
            }
        }

        return n;
    }
};

题目来源

• 27. Remove Element