Hacker rank Similar Pairs - algorithm

Question

I am trying to solve hacker rank similar pairs https://www.hackerrank.com/contests/101hack/challenges/similarpair problem. I cant figure out why its failing for large test cases. I am using segment trees to solve this problem in nlogn time. You can find my code below.
#include<iostream>
#include<vector>
using namespace std;
vector<int> graph[110001];
int T, ST[100001*4] = {0}, N, deg[100001] = {0};
void update(int node, int b, int e, int idx, int val) {
if(b > node || e < node) return;
if(b == e) {
ST[idx] += val;
return;
}
update(node, b, (b + e)/2, 2 * idx, val);
update(node, (b + e)/2 + 1, e, 2 * idx + 1, val);
ST[idx] = ST[2 * idx] + ST[2 * idx + 1];
}
long Query(int l, int r, int b, int e, int idx) {
if( l > e || r < b) return 0;
if(l <= b && r >= e) return ST[idx];
return Query(l, r, b, (b + e)/2, 2 * idx) + Query(l, r, (b + e)/2 + 1, e, 2 * idx + 1);
}
long long SimilarPairs(int node) {
int l = max(1, node - T), r = min(N, node + T);
long res = 0;
res = Query(l, r, 1, N, 1);
update(node, 1, N, 1, 1);
for(int i = 0; i < graph[node].size(); i++) {
res += SimilarPairs(graph[node][i]);
}
update(node, 1, N, 1, -1);
return res;
}
int main() {
long x, y, root, result, start;
cin >> N >> T;
for(int i = 0; i < N - 1; i++) {
cin >> x >> y;
graph[x].push_back(y);
deg[y]++;
}
for(int i = 1; i <= N; i++) if(!deg[i]) root = i;
result = SimilarPairs(root);
cout << result << endl;
cin.get();
return 0;
}

Answer 1

I get what you were doing. The problem is that you were missing some long longs. long is the same as an int (on 32 bits), so you must use long long everywhere, since the result does not necessarily fit in a 32 bit int.
This gets AC:
#include<iostream>
#include<vector>
using namespace std;
vector<int> graph[110001];
int T, N, deg[100001] = {0};
long long ST[100001*4] = {0};
void update(int node, int b, int e, int idx, int val) {
if(b > node || e < node) return;
if(b == e) {
ST[idx] += val;
return;
}
int m = (b + e) >> 1;
int q = idx << 1;
update(node, b, m, q, val);
update(node, m + 1, e, q + 1, val);
ST[idx] = ST[q] + ST[q+1];
}
long long Query(int l, int r, int b, int e, int idx) {
if( l > e || r < b) return 0;
if(l <= b && r >= e) return ST[idx];
int m = (b + e) >> 1;
int q = idx << 1;
return Query(l, r, b, m, q) + Query(l, r, m + 1, e, q + 1);
}
long long SimilarPairs(int node) {
int l = max(1, node - T), r = min(N, node + T);
long long res = 0;
res = Query(l, r, 1, N, 1);
update(node, 1, N, 1, 1);
for(int i = 0; i < graph[node].size(); i++) {
res += SimilarPairs(graph[node][i]);
}
update(node, 1, N, 1, -1);
return res;
}
int main() {
long x, y, root, start;
cin >> N >> T;
for(int i = 0; i < N - 1; i++) {
cin >> x >> y;
graph[x].push_back(y);
deg[y]++;
}
for(int i = 1; i <= N; i++) if(!deg[i]) root = i;
long long result = SimilarPairs(root);
cout << result << endl;
cin.get();
return 0;
}