Multiplying a numeric string with the “vedic method”

This is vedic method multiplication. This code takes time on a very long numeric string, and I want to optimize it. I also apply recursion on multIndices (this function is multiplying two given indices values).

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

char str1[10000],str2[10000],resultant[10000000];
int carry=0,n=0;
void mulIndices(int i, int j){
    int result=0;
    for(;i<=j;i++,j--){
    result = result + carry + (str1[i]-48)*(str2[j]-48);
        if(i!=j)
            result += (str2[i]-48)*(str1[j]-48);
    carry=0;
    }
    if(result > 9){
        carry = result/10;
        result %= 10;
    }
    resultant[n++] = result+48;
}
void reverseStr(char str[]){
    int tmp,i=0,j=0,length = strlen(str);
    for(i=0,j=length-1;i<length/2;i++,j--){
            tmp = str[i];
            str[i] = str[j];
            str[j] = tmp;
    }
}
int main()
{
    int value=-1, i=0,u,v,j=0,mulVal=0,length1 = 0,length2 = 0,diffOfLen=0,maxLength=0;
    printf("Enter the first numeric value: ");
    gets(str1);
    printf("Enter the second numeric value: ");
    gets(str2);

    length1 = strlen(str1);
    length2 = strlen(str2);

    if(length2<length1){
        diffOfLen= length1-length2;
        maxLength = length2;
    }else{
        diffOfLen= length2-length1;
        maxLength = length1;
    }

    i = diffOfLen;
/*
    if(length2<length1){
        i += length2;
    }else if(length2>length1){
        i += length1;
    }
*/
    reverseStr(str1);
    reverseStr(str2);

    while(diffOfLen--){
        //printf("%d\n",diffOfLen);
        if(length2<length1){
            str2[i++] = '0';
            str2[i] = '\0';
        }
        else if(length2>length1){
            str1[i++] = '0';
            str1[i] = '\0';
        }
    }
/*
    puts(str1);
    puts(str2);
*/



    for(i=0;i<maxLength;i++){
            mulIndices(0,i);
            //printf("0 %d\n",i);
    }
    for(i=1;i<maxLength;i++){
            mulIndices(i,maxLength-1);
            //printf("0 %d\n",i);
    }if(carry != 0){
        resultant[n++] = carry+48;
    }
    resultant[n] = '\0';
    reverseStr(resultant);
    puts(resultant);

    return 0;
}