CodeSignal 刷题 —— almostIncreasingSequence

Given a sequence of integers as an array, determine whether it is possible to obtain a strictly increasing sequence by removing no more than one element from the array.

Example

• For sequence = [1, 3, 2, 1], the output should be
  almostIncreasingSequence(sequence) = false.

  There is no one element in this array that can be removed in order to get a strictly increasing sequence.

• For sequence = [1, 3, 2], the output should be
  almostIncreasingSequence(sequence) = true.

  You can remove 3 from the array to get the strictly increasing sequence [1, 2]. Alternately, you can remove 2 to get the strictly increasing sequence [1, 3].

Input/Output

• [execution time limit] 0.5 seconds (cpp)

• [input] array.integer sequence

  Guaranteed constraints:
  2 ≤ sequence.length ≤ 105,
  -105 ≤ sequence[i] ≤ 105.

• [output] boolean

  • Return true if it is possible to remove one element from the array in order to get a strictly increasing sequence, otherwise return false.

Python3解法：

import copy

def isSequence(lst):
    for i in range(len(lst)):
        if lst.count(lst[i]) > 1:      #如果列表中有重复的数字，返回False
            return False
    sort_lst = copy.copy(lst)
    sort_lst.sort()
    if lst == sort_lst:
        return True
    else:
        return False


def almostIncreasingSequence(sequence):
    if isSequence(sequence):
        return True
    i = 0
    while i < len(sequence):
        sequence_copy = copy.copy(sequence)
        del sequence_copy[i]                   # 循环，一个一个删除，查看剩余序列是否严格递增有序
        if isSequence(sequence_copy):
            return True
        i += 1

    return False

print(almostIncreasingSequence([1,2,1,2]))

C++解法：

bool isSequence(vector<int> sequence)
{
    set<int>iset;
    for(auto e: sequence)
        iset.insert(e);
    if(iset.size() != sequence.size())     //如果sequence中有重复元素，返回false
        return false;

    vector<int>v = sequence;               //如果sequence与排序后的v相等，则说明sequence是递增有序的
    sort(v.begin(), v.end());
    if(sequence == v)
        return true;
    else
        return false;

}

bool almostIncreasingSequence(std::vector<int> sequence) 
{
    if (isSequence(sequence))
        return true;
    int i = 0;
    while (i < sequence.size())
    {
        vector<int> v = sequence;
        v.erase(v.begin() + i);
        if(isSequence(v))
            return true;
        ++i;
    }
    return false;
}