HackerEarth COD love!! [Medium] problem solution

In this HackerEarth COD love!! [Medium] problem solution Gurpreet and Shyamu were playing COD(yes you read right that is Call of Duty). As you all know Gurpreet is too good in it. Shyamu being jealous give Gurpreet a problem to solve so that he can clear more missions than him.

The Problem is :

Shyamu gives Gurpreet a string str and q queries.

Each query is of type

k ch

(where k is a positive number and ch is a lowercase character)

In each query Gurpreet has to delete kth occurence of character ch. And at the end he has to print the string after all queries. As Gurpreet wants to play COD he give this task to you to solve.

#include <stdio.h>
int bit[26][210021];
int pos[26][210021];

char str[210021],ch;
int fq[26];
void update(int ind1, int ind2, int val)
{
    while(ind2 < 210021 )
    {
        bit[ind1][ind2]+=val;
        ind2 += ind2 & (-ind2);
    }
}
int dis(int ind1, int ind2)
{
    int ret = 0;
    while(ind2 > 0)
    {
        ret+= bit[ind1][ind2];
        ind2 -= ind2&(-ind2);
    }
    return ret;
}
int solve(int a, int b)
{
    int prev,ans=0, total=0;
    do
    {
        prev= ans;
        ans = dis(a,b+ans);
        total+= abs(ans-prev);

    }while(prev!=ans);

    return total;
}
int main()
{
    int len;
    scanf("%s%n",str+1,&len);
    for(register int i = 1; i <= len; ++i)
    {
        int key = str[i]-'a';
        pos[key][++fq[key]] = i;
    }
    int q,x;
    scanf("%i",&q);
    for(register int i = 0; i < q; ++i)
    {
        scanf("%i %c",&x,&ch);
        int add = solve(ch-'a',x);
        str[ pos[ch-'a'][x+add]] = -1;
        update(ch-'a', x+add,1);
    }
    for(register int i = 1; i <= len; ++i)
        if(str[i] + 1)
            putchar(str[i]);
    return 0;
}