我的代码编译,执行,但崩溃某些输入

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.提前致谢.

Answer 1

本地声明:

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

int在调用堆栈上分配2500万个字节,即4字节字(100兆字节).在当前台式机和笔记本电脑上,典型的调用堆栈最多只有几兆字节,所以你最好在每个调用框架中使用几千字节(但是YMMV).

您肯定会遇到堆栈溢出.

您可以考虑堆分配的C++ 标准容器,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,时间去学习更多的调试工具:g++ -Wall -Wextra -g,也许还-fsanitize=address的gdb调试器,Valgrind的,strace的.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:C++与编程之旅- 使用C++的原理与实践

如果您在Linux上编码,则高级Linux编程也值得一读.