Remove Element

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.

图解

分析

1. two pointers : slow and fast
2. scan the array from leftmost to rightmost using fast pointer, when nums[fast] is not equal to value, we assign nums[fast] to nums[slow] and increment slow

代码

class Solution {
   public int removeElement(int[] nums, int val) {
      int base = 0;
      for(int i = 0;i<nums.length;i++){
          if(nums[i]!= val){
              nums[base]=nums[i];
              base++;
          }        
      }
       return base;
    }
}