二分法查找

var arr = [1, 2, 3, 4, 5, 6, 7, 8];
var a = 1;
var start = 0;
var end = arr.length - 1;

// 二分法递归方法
function find(arr, a, start, end) {
    var temp = Math.ceil((end + start) / 2);
    if (start > end) {
        console.log('找不到');
        return false;
    }
    if (arr[temp] == a) {
        console.log("找到了");
        return true;
    } else if (arr[temp] > a) {
        end = temp - 1;
        find(arr, a, start, end);
    }
    else if (arr[temp] < a) {
        start = temp + 1;
        find(arr, a, start, end);
    }
}

// 二分法非递归
function find2(arr, a, start, end) {
    while ((end - start) >= 0) {
        var temp = Math.floor((end + start) / 2);
        console.log(temp)
        if (arr[temp] == a) {
            console.log('找到了');
            return true;
        } else if (arr[temp] > a) {
            end = temp - 1;
        } else if (arr[temp] < a) {
            start = temp + 1;
        }
    }
    console.log('找不到');
    return;
}

find(arr, a, start, end);
find2(arr, a, start, end);