Update 1292.cpp

SciEm · SciEm · commit 19b288afd92c · 2022-03-29T16:45:59.000+09:00
diff --git a/0x12/solutions/1292.cpp b/0x12/solutions/1292.cpp
@@ -1,11 +1,23 @@
-// Authored by : BaaaaaaaaaaarkingDog
+// Authored by : SciEm
 // Co-authored by : -
-// http://boj.kr/****************
+// http://boj.kr/2fe6deab624e4c83b409ab234ee8aa48
 #include <bits/stdc++.h>
 using namespace std;
 
-int main(void){
+int func(int n) {
+  int i = 1, sum = 0;
+  while (n > i) sum += i * i, n -= i++;
+  return sum + i * n;
+}
+
+int main() {
   ios::sync_with_stdio(0);
   cin.tie(0);
-  
-}
+
+  int a, b;
+  cin >> a >> b;
+  cout << func(b) - func(a - 1);
+}
+/*
+수열을 (1) (2 2) (3 3 3) ... 과 같이 묶으면 i 번째 군의 합은 i * i임을 이용했다.
+*/
