can anyone tell me what is this code for?
especially this line of code, I can't understand this line
ctr[arr[i] - 1]++;
function array_element_mode(arr) {
var ctr = [],
ans = 0;
for (var i = 0; i < 10; i++) {
ctr.push(0);
}
for (var i = 0; i < arr.length; i++) {
// what is this code for??
ctr[arr[i] - 1]++;
if (ctr[arr[i] - 1] > ctr[ans]) {
ans = arr[i] - 1;
}
}
return ans + 1;
}
console.log(array_element_mode([1, 2, 3, 2, 2, 8, 1, 9]))I believe that this function is supposed to return the mathematical mode of an array.
I just added/fixed some variable names to your function. This is still a terrible implementation but I'm hoping that the edits will make what it does more clear to you.
function array_element_mode2(arr) {
var center = [],
mode = 0;
for (let i = 0; i < 10; i++) {
center.push(0);
}
for (let i = 0; i < arr.length; i++) {
const priorElementOfArr = arr[i] - 1;
center[priorElementOfArr]++;
if (center[priorElementOfArr] > center[mode]) {
mode = priorElementOfArr;
}
}
return mode + 1;
}
I renamed the varibles and splitted ctr[arr[i] - 1]++; into two lines. This functions is supposed to find the number which appears most in a given array of integers.
But it wont work if two or more integers appear the same number of times and if the array contains 0.
/*
* Goal: Find the number which appears most in a given array of integers
* Solution: In the ctr array store the number apperences in the following way
* ctr[0] appearances of "1" in the array
* ctr[1] appearances of "2" in the array
* ctr[2] appearances of "3" in the array
* ...
*/
function array_element_mode(arr) {
var ctr = [],
ans = 0;
// fill the ctr array with nulls
for (var i = 0; i < 10; i++) {
ctr.push(0);
}
for (var i = 0; i < arr.length; i++) {
//////////// here the ctr[arr[i] - 1]++; is splitted into 2 lines
// for each array member "find" the correct index to increase
const convertArrayMemberToIndexForCtr = arr[i] - 1;
// increase the correct index by one
ctr[convertArrayMemberToIndexForCtr]++;
///////////
// check if the increased index if larger then current answer and if so
// store it as the new result
if (ctr[convertArrayMemberToIndexForCtr] > ctr[ans]) {
ans = convertArrayMemberToIndexForCtr;
}
}
// return the result, but not the index we created before (on line 25), but the real number that is in the array (add the +1 we subtracted before)
return ans + 1;
}
console.log('working example');
console.log(array_element_mode([1, 2, 3, 2, 2, 8, 1, 9]));
console.log('this wont work, it shows that "3" is the result, ignoring the "2"');
console.log(array_element_mode([3, 3, 3, 2, 2, 2, 5, 9]));
console.log('this wont work as index arr[i] - 1 would then be 0-1=-1');
console.log(array_element_mode([0, 1, 1, 0, 0, 4, 5, 9]));
console.log('this wont work, all integers are only once in the array');
console.log(array_element_mode([1, 2, 3, 4, 5, 6, 7, 8]));I think this function is to find out which element has the most number in the array
ctr[arr[i] - 1]++：In order to count