rewrite problem47 for more readability

Author: eagletmt

40-49/problem47.c

@@ -8,52 +8,34 @@
 #define N 4
 #define M 1000000
 
+static int distinct_factor_count(unsigned n);
+
 /* this program may take sevaral seconds */
 int main(void)
 {
-  unsigned i;
-  for (i = 2; i < M; i++) {
-    unsigned factors[N][N];
-    unsigned j;
-
-    for (j = 0; j < N; j++) {
-      unsigned c, k, l;
+  unsigned i, j = 0;
+  for (i = 2; i < M && j < N; i++) {
+    for (j = 0; j < N && distinct_factor_count(i+j) == 4; j++)
+      ;
+  }
+  printf("%u\n", i-1);
 
-      for (c = 0; c < N; c++) {
-        factors[j][c] = 1;
-      }
+  return 0;
+}
 
-      /* factorize */
-      k = i+j;
-      l = 2;
-      c = 0;
-      while (k != 1 && c < N) {
-        while (k % l == 0) {
-          k /= l;
-          factors[j][c] *= l;
-        }
-        l++;
-        if (factors[j][c] != 1) {
-          c++;
-        }
-      }
-      if (c != N) {
-        /* too few factors */
-        goto NEXT;
-      }
-      if (k != 1) {
-        /* too many factors */
-        goto NEXT;
+int distinct_factor_count(unsigned n)
+{
+  unsigned count = 0;
+  unsigned i;
+  for (i = 2; i <= n; i++) {
+    if (n % i == 0) {
+      count++;
+      n /= i;
+      while (n % i == 0) {
+        n /= i;
       }
     }
-
-    /* this i is the answer! */
-    printf("%u\n", i);
-    break;
-NEXT:
-    ;
   }
-
-  return 0;
+  return count;
 }