TD: novembre 2019

Map en action

function alphabetRange (start, end, step = 1) {
return new Array(Math.ceil((end.charCodeAt(0) - start.charCodeAt(0))/step))
.fill(start.charCodeAt(0))
.map((x, i) => String.fromCharCode(i*step + start.charCodeAt(0)));
}
console.log(alphabetRange('c', 'h', 2));

String in action

let s = 'abcdefghijklmnopqrstuvwxyz'
s= s.substring(s.indexOf('p'), s.indexOf('t')+ 1);
let A= s.split('');

code

Unique !

Nous allons donner un ensemble de fonction recherchant les valeurs uniques d'un tableau.

let t = [2,0,2,0,2,3];
console.time("time");
unique(t);
console.timeEnd("time");

Nous pourrons comparer le temps d'exécution des différentes propositions de code.

Nous pourrions également integrer un test élémentaire sur le tableau en argument

if (!Array.isArray(arr)) {
throw new TypeError('array-unique expects an array.');
}

Les écritures suivantes ne sont pas commentées

function unique(t){
let cur = t.length;
while (--cur){
for (let i=0; i< cur; i++){
if (t[i] == t[cur]){
t.splice(cur,1);
break;
}
}
}
}

function unique(arr) {
let i = -1;
while (i++ < arr.length) {
var j = i + 1;
for (; j < arr.length; ++j) {
if (arr[i] === arr[j]) {
arr.splice(j--, 1);
}
}
}
return arr;
};

function unique(array) {
let passed = [];
for (let i=0 ; i < array.length; i++) {
if (array.indexOf( array[i]) === i)
passed.push(array[i]);
}
return passed;
}

function unique(t){
let u = t.reduce(function(a,c){
if (!a.includes(c)){
a.push(c)
}
return a;
},[])
return u;
}

function unique(value,index,tab){
return tab.indexOf(value) === index;
}
console.time("while")
t = t.filter(unique);
console.timeEnd("while");

console.time("while")
let v = [...new Set(t)];
console.timeEnd("while");

const T = [
{ name: 'dupont', id:22 },
{ name: 'dupont', id:20 },
{ name: 'dupond', id:21 },
{ name: 'dupond', id:21 },
];
const unique = [];
const map = new Map();
for (const item of T) {
if(!map.has(item.id)){
map.set(item.id, true); // set any value to Map
unique.push({
id: item.id,
name: item.name
});
}
}
console.log(unique)

Projet

Ecrire l'équivalent Js de ce code Python

import random
from collections import Counter
l = [random.randint(0,9) for i in range(10)]
print (l)
print(Counter(l).most_common())
print(Counter(l).most_common(1))

Exemple de résultat
[6, 6, 0, 4, 8, 7, 6, 4, 7, 5]
[(6, 3), (4, 2), (7, 2), (0, 1), (8, 1), (5, 1)]
[(6, 3)]

code

deepCopy

function deepCopy(p, c={}){

for (let i in p){
if (p.hasOwnProperty(i)){
if (typeof p[i] ==="object"){
c[i] = Array.isArray(p[i]) ? [] : {};
deepCopy(p[i], c[i]);
}
else {
c[i] = p[i];
}
}
}
return c;

}

let u = [1,[1,2],3];

let c = deepCopy(u);

console.log(u);

code

Range : bad idea

Définition de la fonction range. lecture

passage des paramètres

Ecrire les valeurs affichées

const testPassagePara = function(args) {

let start = args;

return [start];

}

console.log(testPassagePara(1))

//-------------------------------------------

const testPassagePara = function(args) {

let start = args;

return [start];

}

console.log(testPassagePara())

//-------------------------------------------
const testPassagePara = function(args=-1) {

let start = args;

return [start];

}

console.log(testPassagePara())

//-------------------------------------------
const testPassagePara = function(...args) {

let [start,end,step] = args;

return [start,end,step];

}
console.log(testPassagePara(1, 5, 2, -1))

//-------------------------------------------
const testPassagePara = function(...args) {

let [start,end,step] = args;

return {start,end,step};
}

console.log(testPassagePara(1, 5, 2, -1))

//-------------------------------------------
const testPassagePara = function(...args) {

let [start,end,step] = args;

return {start,end,step};
}

console.log(testPassagePara(1))

//-------------------------------------------
const testPassagePara = function(...args) {

let [start=0,end=0,step=1] = args;

return [start,end,step];
}

console.log(testPassagePara(1))

nb occurence

const words = [1,2,7];

const alphabetical = words.reduce((a, x) => {
if (!a[x]) a[x] = 0;
a[x]=a[x]+1;
return a},{});

-----------------------

const alphabetical = words.reduce((a, x) => {
if (!a[x]) a[x] = 0;
a[x]=a[x]+1;
return a},[]);

-----------------------

const words = [1,2,2,1,5];

let min = words.reduce((a, x) => Math.min(a,x));

console.log(min);

let max = words.reduce((a, x) => Math.max(a,x));

console.log(max);

let t = Array.from({length:max-min+1},()=>0);

console.log(t);

const alphabetical = words.reduce((a, x) => {
a[x-1]= a[x-1]+1;
return a},t);

--------------------------------

const words = [1,2,2,1,5];

let minMaxDistSumMoyNb = words.reduce((a, x) => {
let [m,M] = [Math.min(a[0],x),Math.max(a[1],x)];
let sum = a[3]+x;
let nb = a[5]+1;
let moy = sum/nb;
return [m,M,M-m+1,sum,moy,nb]
}
,[Number.MAX_VALUE,Number.MIN_VALUE,Number.MIN_VALUE,0,0,0]);

console.log(minMaxDistSumMoyNb);

Trier en multicritère

Code

swap

en C

void swap(int *xp, int *yp)
{
int temp = *xp;
*xp = *yp;
*yp = temp;
}

int main()
{
int x=1, y=2;

swap(&x, &y);
printf("x = %d, y = %d", x, y);
return 0;
}

➥ code dans Pythontutor

js

let swap = (x,y) => [y,x];

let x=1, y=2;
[x,y] = swap(x,y);
console.log(`x=${x} y=${y}`)

➥ code dans Pythontutor

Les pointeurs et les tableaux !

Visualisation et parcours dans un tableau

Aide TD max col

let TAB_MAX_Value = TAB.reduce((max_val,lig_val)=> Math.max(max_val,Math.max(...(lig_val))),Number.MIN_VALUE);

// ecriture => let TAB_Min = TAB.reduce((m,l) => Math.min(m,Math.min(...(l))),TAB[0][0]);

code source

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