Longest Common Subsequence(Question-3_Spring2011)

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int findmax(char **commons, int size) {
    int i, max=0, maxPlace;
    //Find The Longest String
    for(i=0;i<size;i++) {
        if(strlen(commons[i]) > max) {
            max = strlen(commons[i]);
            maxPlace = i;
        }
    }
    return maxPlace; // Return The Longest String Index
}

char *strdupCommons(char *str, int flag)
{
    int i;
    char *ptr;

    if(flag) { //We Need Shorter String
        // Customized Strdup
        for(i=0;i<strlen(str)-1;i++)
            ptr = (char *)malloc( (i+1) * sizeof(char) );

        ptr[i]='\0';
        for(i-=1;i>=0;i--)
            ptr[i]=str[i];
    }
    else {    // Near The End We Dont Need Shorter String
        ptr = strdup(str); // Regular Strdup
    }

    return ptr;
}

void main() {
    char str1[] = "C exam question 3 fall 2011";
    char str2[] = "C program exam fall 2011 questions";
    char **commons = NULL;  // Commons String Array
    char temp[100];         // Temporary String
    int flag = 0;           // 0 - UnCommon / 1 - Common
    int i, j = 0, comi = 0; // Indexes

    for(i=0;str1[i]!='\0';i++) { // Run On Str1
        strncpy(temp,&str1[j],i+1); // Copy Str1(From Place j To i+1) To Temp - SubString
        temp[i+1]='\0'; // Close The SubString
        if(strstr(str2,temp) != NULL && str1[i+1]!='\0') // Check If The SubString Exist On Str2
            flag=1;
        else if(flag==1) { // Not Exist Anymore But Was Exist
            commons = (char **) realloc(commons, (comi+1) * sizeof(char *)); //Allocate Memory For Strings Array
            if(str1[i+1]!='\0') // Check If We Near The End, Send Flag 1 To strdupCommons
                commons[comi] = strdupCommons(temp,1);
            else // Send Flag 0 To strdupCommons
                commons[comi] = strdupCommons(temp,0);
            comi++; // Make The Commons Index(For The Strings Array) Bigger;
            flag = 0; // Flag Is On UnCommon State
            j=i; // j is now like i (Start Substring from j)
            //puts(commons[comi-1]); //Print The Common Strings
        }
        else
            j=i; // j is now like i (Start Substring from j)
    }
    printf("Longest Common Subsequence Is: %s With %d Chars\n", commons[findmax(commons,comi)], strlen(commons[findmax(commons,comi)]) );
}