求2数之和

# 暴力算法
def func1(li: list, target: int):
    for i in range(len(li)):
        for j in range(i + 1, len(li)):
            if li[i] + li[j] == target:
                return i, j
    return -1, -1


# 字典转换
def func2(li: list, target: int):
    temp = {}
    for i in range(len(li)):
        if temp.get(target - li[i], -1) > 0:
            return temp.get(target - li[i]), i
        temp[li[i]] = i
    return temp.get(target - li[i], -1), -1


# 二分查找, 需要list已有序
def func3(li: list, target: int):
    # li.sort()
    for i in range(len(li)):
        temp = target - li[i]
        low = i+1
        high = len(li) - 1
        while low <= high:
            mid = (low + high) // 2
            if li[mid] == temp:
                return i, mid
            elif li[mid] < temp:
                low = mid + 1
            else:
                high = mid - 1
    return -1, -1


# 双指针, 需要list已有序
def func4(li: list, target: int):
    # li.sort()
    low = 0
    high = len(li) - 1
    while low <= high:
        if li[low] + li[high] == target:
            return low, high
        elif li[low] + li[high] < target:
            low += 1
        else:
            high -= 1
    return -1, -1


if __name__ == '__main__':
    li = [1, 2, 3, 4, 5, 6, 7, 8, 9]
    target = 17
    print(func1(li, target))
    print(func2(li, target))
    print(func3(li, target))
    print(func4(li, target))