插入排序及使用二分查找优化

function insertSrot(arr){
            if (arr == null || arr.length < 2) {
                return arr;
            }
            var len = arr.length;
            var preIndex, current;
            for (var i = 1; i < len; i++) {
                preIndex = i - 1;
                current = arr[i];
                while (preIndex >= 0 && arr[preIndex] > current) {
                    arr[preIndex + 1] = arr[preIndex];
                    preIndex--;
                }
                arr[preIndex + 1] = current;
            }
            return arr;
        }

        function insertSrot1(arr) {
            window.count1 = 0;
            if (arr == null || arr.length < 2) {
                return arr;
            }
            var len = arr.length;
            for (var i = 1; i < len; i++) {
                for(var j = i-1;j>=0;j--){
                    window.count1++;
                    if(arr[j+1]<arr[j]){
                        var temp = arr[j+1];
                        arr[j+1] = arr[j];
                        arr[j] = temp;
                    }
                }
            }
            console.log('未使用二分优化的计算次数',window.count1)
            return arr;
        }



        //2分查找
        function binary_search(arr, key) {
                var low = 0,
                    high = arr.length - 1;
                while (low <= high) {
                    window.count++;
                    var mid = parseInt((high + low) / 2);
                    if (key == arr[mid]) {
                        return mid;
                    } else if (key > arr[mid]) {
                        low = mid + 1;
                    } else if (key < arr[mid]) {
                        high = mid - 1;
                    }

                    if (key > arr[mid] && key < arr[mid + 1]) {
                        return mid;
                    }else if(key<arr[0]){
                        return -1;
                    }else if(key>arr[high]){
                        return high;
                    }
                }
            };
        // console.error(binary_search([2,12], 13))
        // console.error(binary_search([2, 12], 1))
        // console.error(binary_search([2,12], 12))
        console.error(binary_search([2], 1))
        // console.error(binary_search([1,2,5,11,12,17,21,29,333,1110,3222],999))
        //插入排序优化，即将比较改为二分查找
        function insertSrot2(arr) {
            if (arr == null || arr.length < 2) {
                return arr;
            }
            var len = arr.length;
            window.count = 0;
            for (var i = 1; i < len; i++) {
                let ind = binary_search(arr.slice(0,i),arr[i]);

                // console.log('ind', ind)
                // console.log('arr[i]', arr[i])
                // console.log('arr', arr.slice(0, i))
                let current =  arr[i];
                for (let j = i-1; j >= ind; j--) {
                    window.count++;
                    arr[j + 1] = arr[j];
                }
                if (ind < 0) {
                    arr[0] = current
                }
                else{
                    arr[ind+1] = current;
                }
            }
            console.log('优化后的计算次数',count)
            return arr;
        }

        let arr1 = [12,2,31,21,245,21,2,4,5,332,788,09,980]
        let arr2 = [12,2]
        // console.log(window.insertSrot(arr1))
        // console.log(window.insertSrot1(arr1))
        // console.log(window.insertSrot2([12,2,31]))
        console.log(window.insertSrot2(arr1))

 这次主要对插入排序的查找使用了二分查找进行优化，对比优化前后的次数，发现还是很有效果的~