function twoSum(nums: number[], target: number): number[] {
    const map = new Map();
    for(let i = 0; i < nums.length; i++) {
        if(map.has(target - nums[i])) {
            return [map.get(target - nums[i]), i];
        } else {
            map.set(nums[i], i);
        }
    }
    return []
}

console.log(twoSum([1, 2, 3, 4, 5], 3))

class DFS
{
   public dfs(G: DFSGraph, startVert: number)
   {
       let visited: boolean[] = Array<boolean>();
       // Pre-populate array:
       for(let i = 0; i < G.size; i++)
       {
           visited.push(false);
       }

       let s: number[] = new Array();

       visited[startVert] = true;

       s.push(startVert);

       while(s.length > 0)
       {
           const v = s.pop();
           for(let adjV of G.adj[v])
           {
               if(!visited[adjV])
               {
                   visited[adjV] = true;
                   s.push(adjV);
               }
           }
       }
   }

   public dfsRecursive(G: DFSGraph, startVert: number)
   {
       let visited: boolean[] = Array<boolean>();
       // Pre-populate array:
       for(let i = 0; i < G.size; i++)
       {
           visited.push(false);
       }
       this.dfsAux(G, startVert, visited);
   }

   private dfsAux(G: DFSGraph, v: number, visited: boolean[])
   {
       visited[v] = true;
       for(let adjV of G.adj[v])
       {
           if(!visited[adjV])
           {
               // this.foo(); // Something can happen before the visit.
               this.dfsAux(G, adjV, visited);
               // this.bar(); // Something can happen after the visit.
           }
       }
   }
}

class DFS
{
   public dfs(G: DFSGraph, startVert: number)
   {
       let visited: boolean[] = Array<boolean>();
       // Pre-populate array:
       for(let i = 0; i < G.size; i++)
       {
           visited.push(false);
       }

       let s: number[] = new Array();

       visited[startVert] = true;

       s.push(startVert);

       while(s.length > 0)
       {
           const v = s.pop();
           for(let adjV of G.adj[v])
           {
               if(!visited[adjV])
               {
                   visited[adjV] = true;
                   s.push(adjV);
               }
           }
       }
   }

   public dfsRecursive(G: DFSGraph, startVert: number)
   {
       let visited: boolean[] = Array<boolean>();
       // Pre-populate array:
       for(let i = 0; i < G.size; i++)
       {
           visited.push(false);
       }
       this.dfsAux(G, startVert, visited);
   }

   private dfsAux(G: DFSGraph, v: number, visited: boolean[])
   {
       visited[v] = true;
       for(let adjV of G.adj[v])
       {
           if(!visited[adjV])
           {
               // this.foo(); // Something can happen before the visit.
               this.dfsAux(G, adjV, visited);
               // this.bar(); // Something can happen after the visit.
           }
       }
   }
}

const getFollowers = async (req: Request, res: Response) => {
  try {
    const username = req.params.username || '';

    const user = await User.findUnique({
      where: { username },
      include: { followedBy: true },
    });

    if (!user) {
      res.status(404).json({
        error: 'User could not be found',
      });
      return;
    }

    const followers = user.followedBy.map(followedBy => {
      return {
        followerId: followedBy.followerId,
      };
    });

    const followersCount = followers.length;

    res.json({ followersCount: followersCount, followers });
  } catch (error) {
    console.error('getFollowers() error: ', error);
    res.status(500).json({
      error: `There was an error fetching followers for user with username "${req.params.username}", please try again later`,
    });
  }
};

const getFollowing = async (req: Request, res: Response) => {
  try {
    const username = req.params.username || '';

    const user = await User.findUnique({
      where: { username },
      include: { following: true },
    });

    if (!user) {
      res.status(404).json({
        error: 'User could not be found',
      });
      return;
    }

    const following = user.following.map(following => {
      return {
        followingId: following.followingId,
      };
    });

    const followingCount = following.length;

    res.json({ followingCount: followingCount, following });
  } catch (error) {
    console.error('getFollowing() error: ', error);
    res.status(500).json({
      error: `There was an error fetching who is following "${req.params.username}", please try again later`,
    });
  }
};

const followUser = async (req: Request, res: Response) => {
  try {
    const username = req.params.username || '';

    const user = await User.findUnique({
      where: { username },
    });

    if (!user) {
      res.status(404).json({
        error: 'User could not be found',
      });
      return;
    }

    // dont allow a user to follow themselves
    if (req.user.id === user.id) {
      res.status(400).json({ error: 'You cannot follow yourself' });
      return;
    }

    //check if a follow relationship already exists
    const followrelationship = await prisma.follows.findUnique({
      where: {
        followerId_followingId: {
          followerId: req.user.id,
          followingId: user.id,
        },
      },
    });

    // check if the follow relationship already exists
    if (followrelationship) {
      res.status(400).json({ error: 'You are already following this user' });
      return;
    }

    // create the follow relationship
    const follow = await prisma.follows.create({
      data: {
        followerId: req.user.id,
        followingId: user.id,
      },
    });

    res.json({ follow });
  } catch (error) {
    console.error('followUser() error: ', error);
    res.status(500).json({
      error: `There was an error following "${req.params.username}", please try again later`,
    });
  }
};

const unfollowUser = async (req: Request, res: Response) => {
  try {
    const username = req.params.username || '';

    const user = await User.findUnique({
      where: { username },
    });

    if (!user) {
      res.status(404).json({
        error: 'User could not be found',
      });
      return;
    }

    // dont allow a user to unfollow themselves
    if (req.user.id === user.id) {
      res.status(400).json({ error: 'You cannot unfollow yourself' });
      return;
    }

    //check if a follow relationship already exists
    const followrelationship = await prisma.follows.findUnique({
      where: {
        followerId_followingId: {
          followerId: req.user.id,
          followingId: user.id,
        },
      },
    });

    // check if the follow relationship already exists
    if (!followrelationship) {
      res.status(400).json({ error: 'You are not following this user' });
      return;
    }

    // delete the follow relationship
    const follow = await prisma.follows.delete({
      where: {
        followerId_followingId: {
          followerId: req.user.id,
          followingId: user.id,
        },
      },
    });

    res.json({ follow });
  } catch (error) {
    console.error('unfollowUser() error: ', error);
    res.status(500).json({
      error: `There was an error unfollowing "${req.params.username}", please try again later`,
    });
  }
};

import React, { useEffect, useRef, useState } from 'react';
import * as d3 from 'd3';

export default function useD3(renderChartFn : (svg : d3.Selection<SVGElement,{},HTMLElement>) => any, dependencies : any[]) {
    const ref = useRef<SVGSVGElement>();

    useEffect(() => {
      let d3El = d3.select(ref.current)
        renderChartFn(d3.select(ref.current));
        return () => {};
      }, dependencies);
    return ref;
}

function MyChart(props : {
    w: number,
    h: number,
    data: Array<any>
}) {
    const [currentData,setCurrentData] = useState(props.data)

    let svgRef = useD3((svg) => {
        if (props.data === currentData) return
        setCurrentData(props.data)
        // add d3 code
        svg.selectAll("*").remove();

        const margin = { top: 0, right: 80, bottom: 20, left: 10 };

        const width = props.w - margin.left - margin.right;
        const height = props.h - margin.top - margin.bottom;

        const canvas = svg
            .attr('width', width + margin.left + margin.right)
            .attr('height', height + margin.top + margin.bottom)
            .append('g')
            .attr('transform', `translate(${margin.left},${margin.top})`);

        // data

        const data = props.data
    },[props])

    return (<svg ref={svgRef} />)
}

function removeElement(nums: number[], val: number): number {
    let zeroStartIndex = 0;
    for(let i = 0; i < nums.length; i++) {
        if(nums[i] !== val) {
            nums[zeroStartIndex] = nums[i];
            zeroStartIndex++;
        }
    }
    return zeroStartIndex;
};