java codility training Genomic-range-query

Question

The task is:

A non-empty zero-indexed string S is given. String S consists of N characters from the set of upper-case English letters A, C, G, T.

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Answer 1

Here is my solution Using Segment Tree O(n)+O(log n)+O(M) time

public class DNAseq {


public static void main(String[] args) {
    String S="CAGCCTA";
    int[] P={2, 5, 0};
    int[] Q={4, 5, 6};
    int [] results=solution(S,P,Q);
    System.out.println(results[0]);
}

static class segmentNode{
    int l;
    int r;
    int min;
    segmentNode left;
    segmentNode right;
}



public static segmentNode buildTree(int[] arr,int l,int r){
    if(l==r){
        segmentNode n=new segmentNode();
        n.l=l;
        n.r=r;
        n.min=arr[l];
        return n;
    }
    int mid=l+(r-l)/2;
    segmentNode le=buildTree(arr,l,mid);
    segmentNode re=buildTree(arr,mid+1,r);
    segmentNode root=new segmentNode();
    root.left=le;
    root.right=re;
    root.l=le.l;
    root.r=re.r;

    root.min=Math.min(le.min,re.min);

    return root;
}

public static int getMin(segmentNode root,int l,int r){
    if(root.l>r || root.r=l&& root.r<=r) {
        return root.min;
    }
    return Math.min(getMin(root.left,l,r),getMin(root.right,l,r));
}
public static int[] solution(String S, int[] P, int[] Q) {
    int[] arr=new int[S.length()];
    for(int i=0;i