array reivew

Array

introduction
- 1D Array:Array is a container for storing multiple item of same type. * 2D Array: if the sub containers also is a same type sub containers.

1 2	1. int [] array = new int[length]; 2. int [] array = new int [] {1,2,3};

2D array: same but have two square bracket

unsorted array method

add() with bug


public static int [] arrayAdd(int [] A, int target) {
        int [] res = new int [A.length+1];
        int idx = 0;
        for (int a : A){
            res[idx++] = a;
        }
        res[A.length] = target;
        A = res;
        return A;
    }
//(2)
    public static int [] arrayAddidx(int [] A, int target, int idx) {
        int [] res= new int [A.length+1];
        if (idx > A.length-1 || idx < 0) {
            System.out.println("Wrong index. ..");
            return A;
        }
        for (int i = 0; i< idx; i++) {
            res[i]=A[i];
        }
        res[idx] = target;
        for (int j = idx; j< A.length; j++) {
            res[j+1]=A[j];
        }
        A  = res;
        return A;
        }

contains() with bug

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public static int contains(int [] A, int target) {
        int index = 0;
        for (Integer a: A) {
            if (a.equals(target)){
                return index;
            }
            else {
                index++;
            }
        }
        return -1;
    }






* modify() with bug





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public static boolean (int [] A, int idx, int target) {
        boolean istrue=false;
        if (idx > A.length - 1 || idx < 0) {
            return istrue;
        }
        A[idx]= target;
        return A[idx]== target;

    }






8 delete() with bug





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public static int [] delete (int [] A, int target) {
        boolean isdelete = false;
        int n = A.length;
        if (contains (A, target) != -1) {
            int i;
            for (i = 0; i < n; i++) {
                if (A[i]==target) {
                    break;
                }
            }
            if (i < n) {
                n = n - 1;
                for (int j = i; j< n; j++) {
                    A[j] = A[j+1];
                }
            }
        }
        int k=0;
        int [] res= new int[A.length - 1];
        for (int a : A) {
            if (k<=A.length - 2) {
                res[k++]=a;
            }
        }
        A = res;
        return A;
    }







DataScale

* O(n)-> 10^8
* 


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DataScale

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