@extra-array/bsearch-right/index.js

Binary searches rightmost value in sorted array.

'use strict';

/**
 * Gives same value.
 * @param v a value
 * @returns v
 */
function id(v) {
    return v;
}

/**
 * Compares two values.
 * @param a a value
 * @param b another value
 * @returns a<b: -1, a=b: 0, a>b: 1
 */
function cmp(a, b) {
    return a < b ? -1 : (a > b ? 1 : 0);
}

/**
 * Binary searches rightmost value in sorted array.
 * @param x an array (sorted)
 * @param v search value
 * @param fc compare function (a, b)
 * @param fm map function (v, i, x)
 * @returns last index of value | ~(index of closest value)
 */
function bsearchRight(x, v, fc = null, fm = null) {
    var fc = fc || cmp, fm = fm || id;
    var v1 = fm(v, 0, null);
    for (var i = 0, I = x.length; i < I;) {
        var m = i + I >>> 1;
        var u1 = fm(x[m], m, x);
        var c = fc(u1, v1);
        if (c <= 0)
            i = m + 1;
        else
            I = m;
    }
    return i <= 0 || fc(fm(x[i - 1], i - 1, x), v1) !== 0 ? ~i : i - 1;
}

module.exports = bsearchRight;