堆和堆排序

堆數據結構

最大堆：是一個徹底二叉樹，全部子節點都不大於父節點

最小對：是一顆徹底二叉樹，全部子節點都不小於父節點

用數組存儲：i的父節點是Math.floor(i/2)

i的左孩子節點是2*i

i的右孩子節點是2*i+1

從index=1開始存儲值

 1 let maxHeap = {
 2     heap:[],
 3     heapPop:function(){
 4         let del = maxHeap.heap[1];
 5         maxHeap.heap[1] = maxHeap.heap[maxHeap.heap.length-1];
 6         maxHeap.heap.length--;
 7         let k = 1;
 8         while(2*k <= maxHeap.heap.length -1){
 9             let j = 2*k; // heap[j]與heap[k]交換
10             if(j+1 < maxHeap.heap.length -1 && maxHeap.heap[j+1] > maxHeap.heap[j]){
11                 j++;
12             }
13             if(maxHeap[k] >= maxHeap[j]){
14                 break;
15             }
16             let tmp = maxHeap.heap[k];
17             maxHeap.heap[k] = maxHeap.heap[j];
18             maxHeap.heap[j] = tmp;
19             k = j;
20         }
21         console.log(maxHeap.heap);
22         return del;
23     },
24     heapPush:function(item){
25         maxHeap.heap[maxHeap.heap.length+1] = item;
26         let k = maxHeap.heap.length;
27         while(k > 1 && maxHeap.heap[Math.floor(k/2)] < maxHeap.heap[k]){
28             let tmp = maxHeap.heap[k];
29             maxHeap.heap[k] = maxHeap.heap[Math.floor(k/2)];
30             maxHeap.heap[Math.floor(k/2)] = tmp;
31             k = Math.floor(k/2);
32         }
33         return maxHeap.heap;
34     },
35 36 
37 }

二分查找法

僅用於有序的順序表

 1 function binarySearch(arr,target){
 2     let low = 0,
 3         high = arr.length - 1,
 4         mid = Math.floor((low+high)/2);
 5     while(low <= high){
 6         if(arr[mid] === target){
 7             return mid;
 8         }
 9         if(target < arr[mid]){
10             high = mid - 1;
11         }else{
12             low = mid + 1;
13         }
14     }
15     return false;
16 }