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[leetcode] 27. remove element

admin 11月 13, 2020 0

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.

标签：

Array, Two Pointers

分析：

和前一题类似，维护两个指针，一个指向“新”数组的尾部，另一个用于遍历“原”数组。

代码：

class  {
public:
    int removeElement(vector<int>& nums, int val) {
        if (nums.size() == 0) return 0;
        int i = 0, j = 0;
        while (j < nums.size()) {
            if (nums[j++] == val) continue;
            else nums[i++] = nums[j-1];
        }
        return i;
    }
};