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CC-11 : Find integers that are common in 2 out of 3 arrays.

Description:

Given 3 integer arrays arr1, arr2, arr3, find and return integers that are common in all 3 arrays.

Test cases and expected outputs:

Input Parameters Expected outputs
intArray1 = {1,2,3,4,5,6,7,8};
intArray2 = {8, 9,10,11,12};
intArray3 = {14,15,16,17}; 		Common elements in atleast 2 arrays: 8
intArray4 = {-3,-2,-1,0,1,2,3};
intArray5= {-2,-1,0, 1, 2};
intArray6= {-2,-1,0,4,5}; 		Common elements in atleast 2 arrays: : -1,0,-2,1,2

Pseudocode:

The java method should accept following input parameters: arr1(integer array), arr2(integer array), arr3(integer array).
Initialize 4 marker integer constants PRESENT_IN_1st_ARR=1; PRESENT_IN_2nd_ARR=2; PRESENT_IN_3rd_ARR=3; PRESENT_IN_ATLEAST2ARRAYS=4.
Initialize idx to 0. Initialize commonCnt to 0.
Initialize a variable common of type HashMap to hold integers from input arrays as keys, and details of whether they occur in multiple arrays as the values.
Iterate through arr1 using a for loop with idx as a loop variable with initial value 0 and increment idx till it reaches arr1.length-1:
add arr1[idx] as key and PRESENT_IN_1st_ARR as value in common.
Iterate through arr2 using a for loop with idx as a loop variable with initial value 0 and increment idx till it reaches arr2.length-1:
If common does not contain key arr2[idx], then put key-value pair arr2[idx] and PRESENT_IN_2nd_ARR to common.
If common contains key arr2[idx] with value PRESENT_IN_1st_ARR, then put key-value pair arr2[idx] and PRESENT_IN_ATLEAST2ARRAYS to common.
Iterate through arr3 using a for loop with idx as a loop variable with initial value 0 and increment idx till it reaches arr3.length-1:
If common does not contain key arr3[idx], then put key-value pair arr3[idx] and PRESENT_IN_3rd_ARR to common.
If common contains key arr3[idx] with value PRESENT_IN_1st_ARR or PRESENT_IN_2nd_ARR, then put key-value pair arr3[idx] and PRESENT_IN_ATLEAST2ARRAYS to common.
After above loop completes successfully, iterate through keys of common and identify keys that have value PRESENT_IN_ATLEAST2ARRAYS and move these keys to an integer array commonArr. Return commonArr.

Code:

public int[] hashMapCommonIn2OutOf3Arrays(int[] arr1,int[] arr2,int[] arr3) throws Exception{
	int PRESENT_IN_1st_ARR=1;
	int PRESENT_IN_2nd_ARR=2;
	int PRESENT_IN_3rd_ARR=3;
	int PRESENT_IN_ATLEAST2ARRAYS=4;
	int idx=0, commonCnt=0;
	HashMap <Integer, Integer> common=new HashMap <Integer, Integer>();
	for (idx=0; idx < arr1.length; idx++) {
		common.put(arr1[idx],PRESENT_IN_1st_ARR);
	}
	int chkCommon=0;
	for (idx=0; idx < arr2.length; idx++) {
		chkCommon=common.getOrDefault(arr2[idx],0);
		if (chkCommon==0) {
			common.put(arr2[idx],PRESENT_IN_2nd_ARR);
		}else {
			if (chkCommon==PRESENT_IN_1st_ARR) {
				common.put(arr2[idx],PRESENT_IN_ATLEAST2ARRAYS);
				commonCnt++;
			}
		}
	}
	chkCommon=0;
	for (idx=0; idx < arr3.length; idx++) {
		chkCommon=common.getOrDefault(arr3[idx],0);
		if (chkCommon==0) {
			common.put(arr3[idx],PRESENT_IN_3rd_ARR);
		}else {
			if ((common.get(arr3[idx])==PRESENT_IN_1st_ARR)||
					(common.get(arr3[idx])==PRESENT_IN_2nd_ARR)) {
				common.put(arr3[idx],PRESENT_IN_ATLEAST2ARRAYS);
				commonCnt++;
			}
		}
	}
	int[] commonArr=new int[commonCnt];
	Iterator itr=common.keySet().iterator();
	int num=0; idx=0;
	while (itr.hasNext()) {
		num=((Integer)itr.next()).intValue();
		chkCommon=common.get(num);
		if (chkCommon==PRESENT_IN_ATLEAST2ARRAYS) {
			commonArr[idx]=num;
			idx++;
		}
	}
	return commonArr;
}

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