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 []
}

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;
};

import { useState, useEffect, useRef } from "react";
// Usage
function App() {
  // State value and setter for our example
  const [count, setCount] = useState(0);
  // Get the previous value (was passed into hook on last render)
  const prevCount = usePrevious(count);
  // Display both current and previous count value
  return (
    <div>
      <h1>
        Now: {count}, before: {prevCount}
      </h1>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
}
// Hook
function usePrevious(value) {
  // The ref object is a generic container whose current property is mutable ...
  // ... and can hold any value, similar to an instance property on a class
  const ref = useRef();
  // Store current value in ref
  useEffect(() => {
    ref.current = value;
  }, [value]); // Only re-run if value changes
  // Return previous value (happens before update in useEffect above)
  return ref.current;
}

// This function takes a matrix and outputs 4 equal size submatrices, starting from top left going to bottom right.
const split = (matrix: number[][]): number[][][] => {
	const n: number = matrix.length
	const mid: number = n/2 
	
	const C11: number[][] = new Array<Array<number>> // first n/2 rows intersection first n/2 columms
	const C12: number[][] = new Array<Array<number>> // first n/2 rows intersection last n/2 columns
	const C21: number[][] = new Array<Array<number>> // last n/2 rows intersection first n/2 columns
	const C22: number[][] = new Array<Array<number>> // last n/2 rows intersection last n/2 columns

	for(let i: number = 0; i < mid; i++) {
	C11.push([])
	C12.push([])
	
	for (let j: number = 0; j < mid; j++) {
	C11[i].push(matrix[i][j])
	}

	for (let j: number = mid; j < n; j++) {
	C12[i].push(matrix[i][j])
	}
	}

	for(let i: number = 0; i < mid; i++) {
	C21.push([])
	C22.push([])
	
	for (let j: number = 0; j < mid; j++) {
	C21[i].push(matrix[i+mid][j])
	}

	for (let j: number = mid; j < n; j++) {
	C22[i].push(matrix[i+mid][j])
	}
	}

	return [C11, C12, C21, C22]
}


// This function takes 4 matrices, in order from top left to bottom right, and combines them into one matrix
const combine = (A: number[][], B: number[][], C: number[][], D: number[][]): number[][] => {

	const n: number = A.length*2
	const combo: number[][] = new Array<Array<number>>

	// Populate combo with temporary 0s
	for(let i: number = 0; i < A.length; i++) {
	combo.push([])

	for (let j: number = 0; j < A.length; j++) {
	combo[i].push(A[i][j])
	}

	for (let j: number = A.length; j < n; j++) {
	combo[i].push(B[i][j-A.length])
	}
	}

	for(let i: number = A.length; i < n; i++) {
	combo.push([])

	for (let j: number = 0; j < A.length; j++) {
	combo[i].push(C[i-A.length][j])
	}

	for (let j: number = A.length; j < n; j++) {
	combo[i].push(D[i-A.length][j-A.length])
	}
	}
	
	return combo
}

// Basic matrix addition function
const matrix_add = (A: number[][], B: number[][]): number[][] => {
	const matrix_sum: number[][] = [[]]
	const n: number = A.length

	for(let i: number = 0; i < n; i++) {
	matrix_sum[i] = []
	for (let j: number = 0; j < n; j++) {
	matrix_sum[i][j] = A[i][j] + B[i][j]
	}
	}
	
	return matrix_sum
}


// Basic matrix subtraction function
const matrix_subtract = (A: number[][], B: number[][]): number[][] => {
	const matrix_diff: number[][] = [[]]
	const n: number = A.length

	for(let i: number = 0; i < n; i++) {
	matrix_diff[i] = []
	for (let j: number = 0; j < n; j++) {
	matrix_diff[i][j] = A[i][j] - B[i][j]
	}
	}
	
	return matrix_diff
}

const strassen = (A: number[][], B: number[][]): number[][] => {
	const n: number = A.length
	var C: number[][] = [[]]

	// Populate C with temporary 0s
	for(let i: number = 0; i < n; i++) {
	C[i] = []
	for (let j: number = 0; j < n; j++) {
	C[i][j] = 0
	}
	}

	// Once the matrices reach a small enough size, compute using the brute force method
	if (n <= 2) {
	for (let i: number = 0; i < n; i++) {
	for (let j: number = 0; j < n; j++) {
	for (let z: number = 0; z < n; z++) {
	C[i][j] = C[i][j] + (A[i][z]*B[z][j])
	}
	}
	}
	return C
	}

	// Create independent variables from function that returns an array with array destructuring.
	const [a, b, c, d] = split(A)
	const [e, f, g, h] = split(B)

	// Using Strassen's method to calculate 1 less product
	const p1: number[][] = strassen(matrix_add(a, d), matrix_add(e,h))
	const p2: number[][] = strassen(d, matrix_subtract(g, e))
	const p3: number[][] = strassen(matrix_add(a, b), h)
	const p4: number[][] = strassen(matrix_subtract(b, d), matrix_add(g, h))
	const p5: number[][] = strassen(a, matrix_subtract(f, h))
	const p6: number[][] = strassen(matrix_add(c, d), e)
	const p7: number[][] = strassen(matrix_subtract(a, c), matrix_add(e, f))

	const C11: number[][] = matrix_add(matrix_subtract(matrix_add(p1, p2), p3), p4)
	const C12: number[][] = matrix_add(p5, p3)
	const C21: number[][] = matrix_add(p6, p2)
	const C22: number[][] = matrix_subtract(matrix_subtract(matrix_add(p5, p1), p6), p7)

	C = combine(C11, C12, C21, C22)

	return C
}

const M1: number[][] = [[1,3],[7,5]]
const M2: number[][] = [[6,8],[4,2]]

const M_Product: number[][] = strassen(M1, M2)

console.log("Matrix 1:")
console.log(M1)
console.log("Matrix 2:")
console.log(M2)
console.log("Product: ")
console.log(M_Product)

// Print Hello, World!
console.log("Hello, World!");