二分查找法 Python 实现：

def binary_search(list, item):
  low = 0
  high = len(list)—1
  while low <= high:
    mid = (low + high) 
    guess = list[mid] 
    if guess == item:
      return mid
    if guess > item:
      high = mid - 1 
    else:
      low = mid + 1
  return None

my_list = [1, 3, 5, 7, 9]

print binary_search(my_list, 3) # => 1
print binary_search(my_list, -1) # => None

二分查找法 JavaScript 实现：

function binary_search(arr, item){
  var left = 0;
  var right = arr.length-1;
  while(left <= right){
    var mid = Math.floor((left+right)/2); 
    if(item == arr[mid]){
      return mid;
    }else if(item > arr[mid]){
      left = mid + 1;
    }else{
      right = mid - 1;
    }
  }
  return false;
}

var arr=[-34, 1, 3, 4, 5, 8, 34, 45, 65, 87];
console.log(binary_search(arr,5));   //4

参考：《算法图解》

修改时间 2023-11-02