分段错误c ++为什么我的程序给我分段错误

Question

Why is my code has segmentation fault? I am trying to see if there is two same letters in a string. But how come it has segmentation fault?

#include<iostream>
#include<cstring>
using namespace std;

bool match(char[], int);

int main()
{
    char word[20];
    cout << "Enter a word: ";
    cin >> word;
    int length = strlen(word);
    if (match(word, length)) cout << "It has two letters that are the same" <<
        endl;
    else cout << "There is no same letters" << endl;
    return 0;
}

bool match(char word[], int length)
{
    bool found = false;
    for (int i = 0; i < length; i++)
    {
        for (int j = 1; i < length; j++)
        {
            if (j <= i || j == length || i == length) continue;
            if (word[i] == word[j]) found = true;
        }
    }
    return found;
}

Answer 1

Did you intentionally include i in your j loop or was that accidental?

Reference:

 "for (int j = 1; i < length; j++)"

Should this be: for (int j; j<length; j++)?

Keep in mind some seg faults have memory management issues, not just logical issues. Check to make sure your sizeof operator is functioning correctly, that's what I usually screw up

Answer 2

There's a typo here:

for (int j = 1; i < length; j++)

where you wrote i instead of j , which means that your loop will never stop.
Reading outside the array is undefined, and by blind luck you got a crash instead of something that appeared to work.

Of the conditions in your inner loop, two are pointless ( j == length and i == length ) because of the loop conditions.
The third only makes you not do anything useful for the first i iterations.
A better way of accomplishing this is to not do anything at all by starting the loop at i + 1 .

bool match(char word[], int length)
{
    for (int i = 0; i < length; i++)
    {
        for (int j = i + 1; j < length; j++)
        {
            if (word[i] == word[j])
            {
                return true;
            }
        }
    }
    return false;
}