2d向量下标超出范围，即使下标在范围内 [英] 2d vector subscripts going out of range even when the subscripts are in range

问题描述

所以我想写一个简单的代码，将从用户的2个字符串。然后它使用length（）获取字符串的长度，并基于长度创建一个ints的矩阵（2d矢量）。然后我需要设置最后一行和最后一列的值具有2的权力值。
如果输入的字符串是happy& sad的结果矩阵应该是：

  0 0 0 0 0 6 
 0 0 0 0 0 4 
 0 0 0 0 0 2 
 10 8 6 4 2 0 
  

生成矩阵如下：

 向量< vector< int>选择; 
 unsigned int x，y; 
 x =（sequenceOne.length（））+ 1; 
 y =（sequenceTwo.length（））+ 1; 
 
 unsigned int p，q; 
 
 opt.resize（y，vector< int>（x，0））; //调整矩阵的大小
  

当我尝试改变矩阵中的值时：

  opt [2] [2] = 5; 
 

它工作正常，但当我去访问最后一行最后一列如下：

  opt [x] [y] 
  

它告诉我表达式：向量下标超出范围
我认为它与获取字符串的长度用作值有关，但我不能我的生活找出为什么会导致一个问题。
我试图使下标不同的变量，不同的顺序，像opt [x-1] [y-1]，但错误仍然出现。

我不确定是否重要，但我使用的是MS VS2012。

解决方案

数组为0索引。 x 和 y 是数组的大小。您不能将大小值用作索引值。

例如：

a 大小为5. a在索引0处，e在索引4处。e列表。当你尝试使用5的大小作为索引，很好没有元素在索引5，你可以看到。最后一个元素将被访问 a [size-1] 。虽然记住，大小为0导致索引为-1，这是一个无效的索引。

So I am trying to write a simple code that will take in 2 strings from the users. It then takes the length of the strings using length() and creates a matrix (2d vector) of ints based on the lengths. I then need to set the values of the last row and last column to have values of powers of 2. If the entered strings are "happy" & "sad" the resulting matrix should be:

0 0 0 0 0 6
0 0 0 0 0 4
0 0 0 0 0 2 
10 8 6 4 2 0 

I am generating the matrix like this:

    vector<vector<int>> opt;
    unsigned int x, y;
    x = (sequenceOne.length()) + 1;
    y = (sequenceTwo.length()) + 1;

    unsigned int p,q;

    opt.resize(y, vector<int>(x, 0)); // resizes the matrix

When I try to change values in the matrix with:

    opt[2][2] = 5;      

It works fine, but when I go to access the last row last column like this:

    opt[x][y]

It tells me "Expression: vector subscript out of range" I think it has something to do with the getting the length of the strings to use as the values, but I can't for the life of me figure out why that would cause an issue. I have tried making the subscripts different variables, different orders, and stuff like opt[x-1][y-1] but the error still occurs.

I'm not sure if it matters but I am using MS VS2012.

解决方案

Arrays are 0 indexed. x and y are the size of the arrays. You can't use the size value as an index value.

For instance:

a is of size 5. "a" is at index 0, "e" is at index 4. "e" is the 5th element in the list. When you try to use the size of 5 as the index, well there is no element at index 5, as you can see. The last element would be accessed a[size - 1]. Though remember, size of 0 results in an index of -1, which is an invalid index.

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