#include <stdio.h>

int lengthOfLongestSubstring(char * s){
    int i = 0;
    char arr[255];
    int max = 0;
    memset(arr, -1, 255);
    int si = 0; //substring start index
    while(s[i] != '\0'){
        if (arr[s[i]] != -1){
            int psi = si;  //previous substring start
            int pi = arr[s[i]]; //previous index of s[i]
            si = pi + 1;  //new substring starts
            int psl = i - psi; //previous substring length
            max = max>psl?max:psl;
            for(int j=psi;j<=pi;j++){
                arr[s[j]] = -1;
            }
        }
        arr[s[i]] = i;
        i++;
       }
    max = max>(i-si)?max:(i-si);
    return max;
}

int main(int argc, char **argv)
{
    //printf("%s\n", argv[1]);
    printf("%d\n", lengthOfLongestSubstring(argv[1]));
    return 0;
}

It gives me runtime error for the input "hijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789hijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789hijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789hijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789hijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789hijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"