LeetCode Js-27. Remove Element

    AllenLi
    LeetCode Js-Array

    Given an integer array nums and an integer val, remove all occurrences of val in nums in-place. The relative order of the elements may be changed.
    If there are k elements after removing the duplicates, then the first k elements of nums should hold the final result. It does not matter what you leave beyond the first k elements.
    Return k after placing the final result in the first k slots of nums.

    在特定的陣列移除val，元素的順序可改，
保留剩下數字，並放置陣列前方。

    Example 1:

    Input: nums = [0,1,2,2,3,0,4,2], val = 2
Output: 5, nums = [0,1,4,0,3,_,_,_]

    Code 1:

    var removeElement = function(nums: number[], val: number): number {
    if (!nums) return 0

    let k = 0

    for (let i = 0; i < nums.length; i++) {
        if (nums[i] !== val) { //如果nums[i]不等於2
            nums[k] = nums[i] //將原陣列的第k個的值，變更成第i個的值
            k++ //k往下一位進行判斷
        }
    }
    return k
};

    FlowChart:

    i = for loop
k = note
remove val = 2

step.1
i =  0                 
    [0,1,2,2,3,0,4,2]  // nums[0] = nums[0]
k =  0                 // next
nums[0]

step.2
i =    1               
    [0,1,2,2,3,0,4,2]  // nums[1] = nums[1]
k =    1               // next
nums[0,1]

step.3
i =      2             
    [0,1,2,2,3,0,4,2]. // remove val
k =      2             // keep k
nums[0,1]

step.4
i =        3           
    [0,1,2,2,3,0,4,2]. // remove val
k =      2             // keep k
nums[0,1]

step.5
i =          4         
    [0,1,2,2,3,0,4,2]. // nums[2] = nums[4]
k =      2             // next 
nums[0,1,3]

step.6
i =            5       
    [0,1,2,2,3,0,4,2]. // nums[3] = nums[5]
k =        3           // next 
nums[0,1,3,0]

step.7
i =              6     
    [0,1,2,2,3,0,4,2]. // nums[4] = nums[6]
k =          4         // next 
nums[0,1,3,0,4]

step.8
i =                7   
    [0,1,2,2,3,0,4,2]. // remove val
k =          4         // next 
nums[0,1,3,0,4]

    Answer:

    Output = [0,1,3,0,4]

    Learning URL

    Code 2:

    var removeElement = function(nums: number[], val: number): number {
    let index = nums.indexOf(val)

    while (index !== -1) {
        nums.splice(index, 1)
        index = nums.indexOf(val)
    }
    return nums.length
};

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