查找数组中两个不连续的元素，且其总和最小

function findMinNonAdjacentPair(a) {
    var mins = [];
    
    // quick exits:
    if (a.length < 5) return {error: "no solution, too few elements."};
    if (a.some(isNaN)) return {error: "non-numeric values given."};
    
    // collect 4 smallest values by their indexes    
    for (var i = 1; i < a.length - 1; i++) { // O(n)
        if (mins.length < 4 || a[i] < a[mins[3]]) {
            // need to keep record of this element in sorted list of 4 elements
            for (var j = Math.min(mins.length - 1, 2); j >= 0; j--) { // O(1)
                if (a[i] >= a[mins[j]]) break;
                mins[j+1] = mins[j];
            }
            mins[j+1] = i;
        }
    }
    // mins now has the indexes to the 4 smallest values

    // Find the smallest sum
    var result = {
        sum: a[mins[mins.length-1]]*2+1 // large enough
    }
    
    for (var j = 0; j < mins.length-1; j++) { // O(1)
        for (var k = j + 1; k < mins.length; k++) {
            if (Math.abs(mins[j] - mins[k]) > 1) { // not adjacent
                if (result.sum    > a[mins[j]]+a[mins[k]]) {
                    result.sum    = a[mins[j]]+a[mins[k]];
                    result.index1 = mins[j];
                    result.index2 = mins[k];
                };
                if (k < j + 3) return result; // cannot be improved
                break; // exit inner loop: it cannot bring improvement
            }
        }
    }
    return result;
}

// Get I/O elements
var input = document.getElementById('in');
var output = document.getElementById('out');
var select = document.getElementById('pre');

function process() {
    // translate input to array of numbers
    var a = input.value.split(',').map(Number);
    // call main function and display returned value
    output.textContent = JSON.stringify(findMinNonAdjacentPair(a), null, 4);
}

// respond to selection from list
select.onchange = function() {
    input.value = select.value;
    process();
}

// respond to change in input box
input.oninput = process;

// and produce result upon load:
process();

Type comma-separated list of values (or select one):</br>
<input id="in" value="2, 2, 1, 2, 4, 2, 6"> &lt;=
<select id="pre">
    <option value="5, 2, 4, 6, 3, 7">5, 2, 4, 6, 3, 7</option>
    <option value="1, 2, 3, 3, 2, 1">1, 2, 3, 3, 2, 1</option>
    <option value="4, 2, 1, 2, 4">4, 2, 1, 2, 4</option>
    <option value="2, 2, 1, 2, 4, 2, 6" selected>2, 2, 1, 2, 4, 2, 6</option>
</select>
</br>
Output:</br>
<pre id="out"></pre>