堆和堆排序

堆数据结构

最大堆：是一个完全二叉树，所有子节点都不大于父节点

最小对：是一颗完全二叉树，所有子节点都不小于父节点

用数组存储：i的父节点是Math.floor(i/2)

i的左孩子节点是2*i

i的右孩子节点是2*i+1

从index=1开始存储值

let maxHeap = {
    heap:[],
    heapPop:function(){
        let del = maxHeap.heap[1];
        maxHeap.heap[1] = maxHeap.heap[maxHeap.heap.length-1];
        maxHeap.heap.length--;
        let k = 1;
        while(2*k <= maxHeap.heap.length -1){
            let j = 2*k; // heap[j]与heap[k]交换
            if(j+1 < maxHeap.heap.length -1 && maxHeap.heap[j+1] > maxHeap.heap[j]){
                j++;
            }
            if(maxHeap[k] >= maxHeap[j]){
                break;
            }
            let tmp = maxHeap.heap[k];
            maxHeap.heap[k] = maxHeap.heap[j];
            maxHeap.heap[j] = tmp;
            k = j;
        }
        console.log(maxHeap.heap);
        return del;
    },
    heapPush:function(item){
        maxHeap.heap[maxHeap.heap.length+1] = item;
        let k = maxHeap.heap.length;
        while(k > 1 && maxHeap.heap[Math.floor(k/2)] < maxHeap.heap[k]){
            let tmp = maxHeap.heap[k];
            maxHeap.heap[k] = maxHeap.heap[Math.floor(k/2)];
            maxHeap.heap[Math.floor(k/2)] = tmp;
            k = Math.floor(k/2);
        }
        return maxHeap.heap;
    },
36 
}

二分查找法

仅用于有序的顺序表

function binarySearch(arr,target){
    let low = 0,
        high = arr.length - 1,
        mid = Math.floor((low+high)/2);
    while(low <= high){
        if(arr[mid] === target){
            return mid;
        }
        if(target < arr[mid]){
            high = mid - 1;
        }else{
            low = mid + 1;
        }
    }
    return false;
}