// -*- mode: typescript; indent-tabs-mode: nil; js-basic-offset: 4 -*-
//
// This file is part of Genie
//
// Copyright 2020 The Board of Trustees of the Leland Stanford Junior University
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Author: Giovanni Campagna <gcampagn@cs.stanford.edu>

export default function binarySearch(cumsum : number[], value : number) : number {
    let a = 0, b = cumsum.length;
    for (;;) {
        if (b - a === 1)
            return a;
        if (b - a === 2) {
            if (value <= cumsum[a])
                return a;
            else
                return a+1;
        }
        const m = Math.floor((a+b)/2);
        if (value <= cumsum[m])
            b = m+1;
        else
            a = m;
    }
}