É MINHA PRIMEIRA VEZ, SEN...SENPAI

#include<bits/stdc++.h>
#define MAXN 100007

using namespace std;

typedef long long int lli;

int arr[MAXN];
lli sgtree[4*MAXN];

void build( int id, int left, int right ) {
    if( left == right ) sgtree[id] = arr[left];
    else {
        int mid = ( left+right ) / 2;
        build( id*2, left, mid );
        build( id*2+1, mid+1, right );
        sgtree[id] = sgtree[id*2] * sgtree[id*2+1];
    }
}

void update( int id, int left, int right, int value, int pos ) {
    if( left == right ) sgtree[id] = value;
    else {
        int mid = ( left + right ) / 2;
        if( pos <= mid ) update( id * 2, left, mid, value, pos );
        else update( id*2+1, mid+1, right, value, pos );
    }
    sgtree[id] = sgtree[id*2] * sgtree[id*2+1];
}

int query( int id, int left, int right, int x, int y ) {
    if( x <= left && right <= y) return sgtree[id];
    else if( y < left || right < x ) return 1;
    else {
        int mid = ( left + right ) / 2;
        return query( id*2, left, mid, x, y) * query( id*2+1, mid+1, right, x, y);
    }
}

int main() {
    int n, k, n1, n2;
    lli mult;
    char letter;

    while( scanf( "%d %d", &n, &k ) != EOF ) {
        string resp = "";
        // memset( arr, 0, sizeof( arr ) );
        // memset( sgtree, 1, sizeof( sgtree ) );
        for( int i = 1; i <= n; i++ ) scanf( "%d", &arr[i] );

        build( 1, 1, n );
        for( int i = 1; i <= k; i++ ) {
            scanf( "%c %d %d", &letter, &n1, &n2 );
            if( letter == 'C' ) update( 1, 1, n, n2, n1 );

            else if( letter == 'P' ) {
                mult = query( 1, 1, n, n1, n2 );
                cout << endl << "O mult é = " << mult << endl;
                if( mult == 0 ) resp += "0";
                else if( mult > 0 ) resp += "+";
                else if( mult < 0 ) resp += "-";
            }
        }
        cout << endl << "RESP = " << resp << endl;
    }
    return 0;
}