Longest string in an array in C++

Question

I wrote this code:

char a[100][100] = {"solol","a","1234567","123","1234"};
int max = -1;
for(int i=0;i<5;i++)
if(max<strlen(a[i]))
max=strlen(a[i]);
cout<<max;

The output it gives is -1.
But when I initialize the value of max by 0, the code works fine.
Why is it so?

Answer 1

Nevermind, I fixed my code myself. I was comparing signed value with an unsigned value returned by strlen(a[i]);