Question

我试图获得两个字符串的最长公共子序列的长度。它适用于大多数输入，但它会针对指定的输入崩溃。代码如下：

#include <cmath>
#include <string>

#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

/* Utility function to get max of 2 integers */
int max(int a, int b)
{
    return (a > b)? a : b;
}

/* Returns length of LCS for X[0..m-1], Y[0..n-1] */
int lcs(string &X, string &Y, int m, int n )
{
    int L[5000 + 1][5000 + 1] = {0};
    int i, j;

    /* Following steps build L[m+1][n+1] in bottom up fashion. Note 
      that L[i][j] contains length of LCS of X[0..i-1] and Y[0..j-1] */
    for (i = 0; i <= m; i++)
    {
        for (j = 0; j <= n; j++)
        {
            if (i == 0 || j == 0)
                L[i][j] = 0;

            else if (X.at(i - 1) == Y.at(j - 1))
                L[i][j] = L[i - 1][j - 1] + 1;

            else
                L[i][j] = max(L[i - 1][j], L[i][j - 1]);
        }
    }

    /* L[m][n] contains length of LCS for X[0..n-1] and Y[0..m-1] */
    return L[m][n];
}

int main() {
    string A, B;
    cin >> A;
    cin >> B;

    int count1 = lcs(A, B, A.size(), B.size());

    cout << count1;
    return 0;
}

输入字符串如下：

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

我尝试使用c风格的字符串，但它崩溃了。如果输入字符串大于阈值但我仍然无效，我也尝试将其分成多个字符串。希望有人找到这个bug。提前谢谢。

Answer 1

本地声明：

    int L[5000 + 1][5000 + 1] = {0};

在调用堆栈上分配2500万int - s，即4字节字（所以100兆字节）。在当前台式机和笔记本电脑上，典型的call stacks最多只有几兆字节，所以你最好在每个调用框架中使用几千字节（但是YMMV）。

您一定会遇到stack overflow。

您可以考虑堆分配的C ++ standard containers，例如std::vector（即使堆栈上有本地容器变量，大多数实际数据都是堆分配的。）

正如我评论的那样，是时候学习更多调试工具了：g++ -Wall -Wextra -g，也许还有-fsanitize=address，gdb调试器，valgrind，strace。细节是特定于实现的。

当然，阅读几本关于C ++ 11（或C ++ 14）的好书：Tour of C++＆amp; Programming - Principles and Practice using C++

如果您在Linux上编码，Advanced Linux Programming也值得一读。

我的代码编译，执行，但崩溃某些输入

1 个答案: