Add : count_triangle cpp

graphs/count_triangle.cpp

@@ -0,0 +1,73 @@
+#include <iostream>
+
+using namespace std;
+
+long long answer = 0;
+int N, M;
+bool map[50][50] = {
+ 0,
+};
+
+void dfs(int start, int current, int before, int depth) {
+ if (depth == 2) {
+ if (current == start) {
+ answer++;
+ }
+ return;
+ }
+
+ int iteration_start, iteration_end;
+ if (depth != 1) {
+ iteration_start = current + 1;
+ iteration_end = N;
+ } else {
+ iteration_start = 0;
+ iteration_end = current;
+ }
+
+ for (int i = iteration_start; i < iteration_end; i++) {
+ if (map[current][i] && i != before) {
+ dfs(start, i, current, depth + 1);
+ }
+ }
+}
+
+void solution() {
+ answer = 0;
+ cin >> N >> M;
+
+ for (int i = 0; i < N; i++) {
+ for (int j = 0; j < N; j++) {
+ map[i][j] = 0;
+ }
+ }
+
+ int x, y;
+ for (int i = 0; i < M; i++) {
+ cin >> x >> y;
+ x--;
+ y--;
+ map[x][y] = 1;
+ map[y][x] = 1;
+ }
+
+ for (int i = 0; i < N - 1; i++) {
+ for (int j = i + 1; j < N; j++) {
+ if (map[i][j]) {
+ dfs(i, j, i, 0);
+ }
+ }
+ }
+
+ cout << "number of triangle : " << answer;
+}
+
+int main() {
+ ios_base ::sync_with_stdio(false);
+ cin.tie(NULL);
+ cout.tie(NULL);
+
+ solution();
+
+ return 0;
+}