查找序列中的下一个最高和最低的数字

Question

How to find the lowest and highest value couples in a sequence of number? I want to save the low/high values of a line graph.

Can you help me with a piece of pseudo code so people can implement the answer in their favorite prog language.

I will be using this to generate a line graph with D3.js. If anybody knows how to do this with D3 I would be more than happy to know about it.

Data Sample: [ 20 , 10, 11, 5 , 15, 25 , 10, 5 , 15, 17, 26 , 15, 7 ]

Desired Result:
array[0][high] = 20
array[0][low] = 5
array[1][high] = 25
array[1][low] = 5
array[2][high] = 26
array[2][low] = 7

This is what I have so far (in Javascript). Do you guys see anyway we can optimize this piece of code?

// data sample
var data_sample = Array(5, 15, 20, 15, 6, 11, 21, 14, 9, 4, 15, 20, 15, 1, 10, 20, 4);

// algo
var low = high = k = 0;
var log = [];

for (var i = 0; i < data_sample.length; i++) {

    var current = data_sample[i];
    var m = i+1;
    var next = data_sample[m];

    if (typeof next == 'undefined') {
        break;
    }

    if (current < next) {
        if (low === 0) {
            low = current;
        } else if (current < low) {
            low = current;
        }
    } else if (current > next && low !== 0) {
        if (high === 0) {
            high = current;
        } else if (current > high) {
            high = current;
        }
    }

    if (low > 0 && high > 0){
        log[k] = [];
        log[k]['low'] = low;
        log[k]['high'] = high;
        k++
        low = high = 0;
    }

};

Thank you in advance

Answer 1

Try this:

var arr = [20, 10, 11, 5, 15, 25, 10, 6, 15, 17, 26, 15, 7],
    sorted = arr.sort(function(a,b){return a-b});

var array = [];

sorted.forEach(function(d,i){
   var s = []; 
   s.push(sorted[i], sorted[(sorted.length-1) - i]);
   array.push(s);
});

console.log(array);

Working fiddle here

Answer 2

The missing part of your code is how to store as array or object.

In your last if condition before you end the for loop you need to initialize log[k] as an object then add the property low and high like this

 if (low > 0 && high > 0){
      log[k] = {};
      log[k].low = low;
      log[k].high = high;
      k++
      low = high = 0;
 }

Doing so will result is

array[0]{high: 20, low: 5}
array[1]{high: 25,low: 6}

If you want it to be an multidimensional array you do it like this: Initialize log[k] as ab empty array.

 if (low > 0 && high > 0){
      log[k] = [];
      log[k]['low'] = low;
      log[k]['high'] = high;
      k++
      low = high = 0;
 }

And the result

array[0]['high'] = 20
array[0]['low'] = 5
array[1]['high'] = 25
array[1]['low'] = 6