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我有一个字符串s = "if man was meant to stay on the ground god would have given us roots"。

我删除了空格并拥有"ifmanwasmeanttostayonthegroundgodwouldhavegivenusroots".

现在我想将字符串的字符推入一个 7 行 8 列的二维向量中。输出应如下所示：

ifmanwas 
meanttos 
tayonthe 
groundgo 
dwouldha 
vegivenu 
sroots

我尝试了以下方法，但没有奏效。

void encryption(string s)
{
    const int rows = 7;
    const int colums = 8;

    vector<vector<char>> v;
    for (int i = 0; i < rows; i++)
    {
        vector<char>temp;
        for (int j = 0; i < colums; j++)
        {
            temp.push_back(s[0]);
            s.erase(0);
        }
        v.push_back(temp);
    }
    for (int i = 0; i < v.size(); i++)
    {
        for (int j = 0; j < v[i].size(); j++)
            cout << v[i][j];
    }
}
4

1 回答 1

1

您的代码有几个问题：

1) 此处循环中使用了错误的索引变量： for (int j = 0; i < colums; j++)

2) 该std::vector::erase函数将迭代器作为参数，而不是位置。

3) 即使你修复了 1) 中提到的循环，你也不会检查你是否在字符串的末尾。

4）您的最终输出不输出回车，使输出看起来“错误”。

给定您使用的字符串，进行适当的更改，代码可能如下所示：

#include <string>
#include <vector>
#include <iostream>

using namespace std;

void encryption(string s)
{
    const int rows = 7;
    const int colums = 8;

    vector<vector<char>> v;
    for (int i = 0; i < rows; i++)
    {
        vector<char>temp;
        for (int j = 0; j < colums && !s.empty(); j++)  // <-- Note we stop the loop if the string is empty.
        {
            temp.push_back(s[0]);
            s.erase(s.begin());  // <-- This erases the first character
        }
        v.push_back(temp);
    }
    for (size_t i = 0; i < v.size(); i++)
    {
        for (size_t j = 0; j < v[i].size(); j++)
            cout << v[i][j];
        cout << "\n";    // <-- You are missing this in your output
    }
}

int main()
{
    encryption("ifmanwasmeanttostayonthegroundgodwouldhavegivenusroots");
}

输出：

ifmanwas
meanttos
tayonthe
groundgo
dwouldha
vegivenu
sroots

鉴于此，这是非常低效的，因为您正在擦除字符串的第一个字符。没有必要为此删除一个字符。

这是一个使用 , 的替代解决方案std::vector<std::string>，以及一个while跟踪字符串中开始和结束迭代器的循环：

#include <string>
#include <vector>
#include <algorithm>
#include <iostream>

void encryption(std::string s)
{
    const size_t columns = 8;

    std::vector<std::string> v;

    // start at beginning of string
    auto startIter = s.begin();

    // point to either 8 characters after the start, or the end of the
    // string, whichever comes first
    auto endIter = startIter + std::min(columns, static_cast<size_t>(std::distance(startIter, s.end())));
    while (true)
    {
        // just push on a string using the start and end iterators
        v.push_back({startIter, endIter});

        // if the end iterator is at the end of the string, quit
        if (endIter == s.end())
            break;

        // move the start to the end
        startIter = endIter;

        // move the end to either 8 characters after the start, or the
        // end of the string, whichever comes first
        endIter = startIter + std::min(columns, static_cast<size_t>(std::distance(startIter, s.end())));
    }

    // Output the results
    for (auto& vrow : v)
        std::cout << vrow << "\n";
}

int main()
{
    encryption("ifmanwasmeanttostayonthegroundgodwouldhavegivenusroots");
}

输出：

ifmanwas
meanttos
tayonthe
groundgo
dwouldha
vegivenu
sroots
于 2019-08-28T01:09:11.960 回答