Google Interview Question for Software Engineers


Country: United States
Interview Type: In-Person




Comment hidden because of low score. Click to expand.
1
of 1 vote

static int[] maxLCS(int[] a, int[] b) {
        int[][] op = new int[a.length + 1][b.length + 1];
        for(int i = 1; i < a.length + 1; i++) {
            for(int j = 1 ;j < b.length + 1; j++) {
                if(a[i-1] == b[j-1]){
                    op[i][j] = op[i-1][j-1] + 1;
                }else {
                    op[i][j] = Math.max(op[i-1][j], op[i][j-1]);
                }
            }
        }
        int maxLen = op[a.length][b.length];
        int[] result = new int[maxLen];
        int ap = a.length;
        int bp = b.length;
        while(ap > 0 && bp > 0) {
            if(a[ap-1] == b[bp-1]) {
                result[maxLen-1] = a[ap-1];
                maxLen--;
                ap--;
                bp--;
            }else if(op[ap-1][bp] <= op[ap][bp-1]) {
                bp--;
            }else {
                ap--;
            }
        }
        return result;
    }

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- acoding167 June 02, 2019 | Flag Reply
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0
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- acoding167 June 02, 2019 | Flag Reply
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0
of 0 vote

// JavaScript version
class LongestCommonSub {
    findSequence(str1, str2) {
        if(!str1 || !str2) throw Error('Invalid input');
        let result = [];
        let op = new Array(str1.length + 1); // the +1 is to store the 0 in the table

        // set the 2D arrays
        for(let i = 0; i <= str1.length; i++) {
            op[i] = new Array(str2.length + 1);
            for(let j = 0; j <= str2.length; j++) {
                op[i][j] = 0;
            }
        }

        for(let i = 1; i < str1.length + 1; i++) {
            for(let j = 1; j < str2.length + 1; j++) {
                if(str1[i-1] === str2[j-1]) {
                    op[i][j] = op[i-1][j-1] + 1;
                }else{
                    // We get the max value between top cell and left cell of current cell
                    op[i][j] = Math.max(op[i-1][j], op[i][j-1]);
                }
            }
        }
        // maxLen is the size of the maximum subsequence
        let maxLen = op[str1.length][str2.length];
        let ap = str1.length;
        let bp = str2.length;
        while(ap > 0 && bp > 0) {
            if(str1[ap-1] == str2[bp-1]) {
                result[maxLen-1] = str1[ap-1];
                maxLen--;
                ap--;
                bp--;
            }else if(op[ap-1][bp] <= op[ap][bp-1]) {
                bp--;
            }else{
                ap--;
            }
        }
        return result;
    }
}

- Danny June 02, 2019 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

@Test
public void test(){
int[] a = new int[]{1,5,2,6,3,7};
int[] b = new int[]{5,6,7,1,2,3,5};

longestSeq(a,b);

System.out.println();


int[] c = new int[]{1,5,2,6,3,4,7};
int[] d = new int[]{5,6,7,1,2,3,5,4};

longestSeq(c,d);
}

class Node{
int index;
int data;
List<Node> kids;

Node(int index, int data){
this.index = index;
this.data = data;
kids = new ArrayList<>();
}
}

private void longestSeq(int[] a, int[] b) {
Node root = seq(a, b);
printLongestPath(root, maxPath(root, 1), new ArrayList<>());

System.out.println();

root = seq(b,a);
printLongestPath(root, maxPath(root, 1), new ArrayList<>());
}

private int maxPath(Node n, int length){
if(n==null) return length;
int max = length;
for (Node kid: n.kids) {
int next = maxPath(kid, length+1);
if(next>max){
max = next;
}
}
return max;
}

private void printLongestPath(Node n, int max, List<Node> list){
if(n==null) return;
list.add(n);
if(list.size()>=max){
list.stream().filter(node-> node.data!=-100).forEach(node -> System.out.print(node.data+" "));
System.out.println();
}
for (Node kid: n.kids) {
printLongestPath(kid, max, list);
}
list.remove(n);
}





private Node seq(int[] a, int[] b) {
Node root = new Node(-100, -100);
for (int i = 0; i < a.length; i++) {
int j = find( a[i], b);
insert2Tree( root , j, a[i]);
}
return root;
}

private void insert2Tree(Node next, int index, int data) {
if(next.index < index) {
for (Node kid : next.kids) {
if(kid.index < index){
insert2Tree(kid, index, data);
return;
}
}
}
next.kids.add(new Node(index, data));

}

private int find(int element, int[] array) {
for (int i = 0 ; i < array.length; i++) {
if(element == array[i]){
return i;
}
}
return -1;
}

- Anonymous June 03, 2019 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

@Test
    public void test(){
        int[] a = new int[]{1,5,2,6,3,7};
        int[] b = new int[]{5,6,7,1,2,3,5};

        longestSeq(a,b);

        System.out.println();


        int[] c = new int[]{1,5,2,6,3,4,7};
        int[] d = new int[]{5,6,7,1,2,3,5,4};

        longestSeq(c,d);
    }

    class Node{
        int index;
        int data;
        List<Node> kids;

        Node(int index, int data){
            this.index = index;
            this.data = data;
            kids = new ArrayList<>();
        }
    }

    private void longestSeq(int[] a, int[] b) {
        Node root = seq(a, b);
        printLongestPath(root,  maxPath(root, 1), new ArrayList<>());

        System.out.println();

        root = seq(b,a);
        printLongestPath(root,  maxPath(root, 1), new ArrayList<>());
    }

    private int maxPath(Node n, int length){
        if(n==null) return length;
        int max = length;
        for (Node kid: n.kids) {
            int next = maxPath(kid, length+1);
            if(next>max){
                max = next;
            }
        }
        return max;
    }

    private void printLongestPath(Node n, int max, List<Node> list){
        if(n==null) return;
        list.add(n);
        if(list.size()>=max){
            list.stream().filter(node-> node.data!=-100).forEach(node -> System.out.print(node.data+" "));
            System.out.println();
        }
        for (Node kid: n.kids) {
            printLongestPath(kid, max, list);
        }
        list.remove(n);
    }





    private Node seq(int[] a, int[] b) {
        Node root = new Node(-100, -100);
        for (int i = 0; i < a.length; i++) {
            int j = find( a[i], b);
            insert2Tree( root , j, a[i]);
        }
        return root;
    }

    private void insert2Tree(Node next, int index, int data) {
        if(next.index < index) {
            for (Node kid : next.kids) {
                if(kid.index < index){
                    insert2Tree(kid, index, data);
                    return;
                }
            }
        }
        next.kids.add(new Node(index, data));

    }

    private int find(int element, int[] array) {
        for (int i = 0 ; i < array.length; i++) {
            if(element == array[i]){
                return i;
            }
        }
        return -1;
    }

- Orasio Spieler June 03, 2019 | Flag Reply


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