Problem 42

42.c

@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <math.h>
+
+bool isPerfectSquare (int n) {
+    int sqrtn = (int) sqrt (n);
+    return sqrtn * sqrtn == n;
+}
+
+bool isTriangular (int n) {
+    return isPerfectSquare (8*n+1);
+}
+
+int main () {
+    FILE* fp = fopen ("p042_words.txt", "r");
+    char file[16 * 1024]; // 16 KiB
+    fgets (file, 16 * 1024, fp);
+
+    int numOfTriangular = 0;
+    char* token = strtok (file, ",");
+    while (token != NULL) {
+        int value = 0;
+        for (int c = 0; c < strlen (token); c++) {
+            if (token[c] >= 'A' && token[c] <= 'Z')
+                value += token[c] - 'A' + 1;
+        }
+
+        if (isTriangular (value)) {
+            numOfTriangular++;
+            printf ("%s: %d\n", token, value);
+        }
+
+        token = strtok (NULL, ",");
+    }
+
+    printf ("%d\n", numOfTriangular);
+}