Python - 两数之和

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给定列表a和一个目标值target，求列表中两数之和为target的值的索引；

a = [1,5,6,8,9,4,5,6,3,2,1,7,5,6,9,8,4,5,6,2,1,0,1,2,0,1,2,5,9,10]
b = [11,55,88,99,66,4,77,33,22,1,6,12,35]

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穷举（适应性强） 

def x(nums,target):
    result = []
    for i in range(len(nums)):
        for j in range(i+1,len(nums)):
            if nums[i]+nums[j] == target:
                result.append((i+1,j+1))
    return result
#print(x(b,10))

双指针（仅限于非重复有序列表的查询）

def y(nums,target):
    result = []
    start = 0
    end = len(nums)-1
    while start < end:
        if nums[start] + nums[end] == target:
            result.append((start+1,end+1))
            end -= 1
            start += 1
        elif nums[start] + nums[end] > target:
            end -= 1
        elif nums[start] + nums[end] < target:
            start += 1
    return result
# print(y(sorted(b),10))

哈希字典查找（仅限于非重复列表的查询）

def z(nums,target):
    result = []
    dict_y = {}
    for i in range(len(nums)):
        m = nums[i]
        if target-m in dict_y:
            result.append((dict_y[target-m]+1,i+1))
        dict_y[m] = i
    return result
#print(z(b,10))

使用字典进行存储（仅限于非重复列表的查询）

def h(nums,target):
    result = []
    xxx = []
    for i in range(len(nums)):
        if target-nums[i] in result:
            xxx.append([result.index(target-nums[i])+1,i+1])
        else:
            result.append(nums[i])
    return xxx
            
print(h(b,10))