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-rw-r--r--ugly_number2.c31
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+// 264. Ugly Number II
+#include "leetcode.h"
+
+/*
+ * an ugly number is a positive integer whose prime factors are limited to
+ * 2,3,5. given an integer 'n', return the n'th ugly number
+ */
+
+int nthUglyNumber(int n) {
+ int *ugly_nums = (int *)malloc(n * sizeof(int));
+ ugly_nums[0] = 1;
+ int idx2 = 0, idx3 = 0, idx5 = 2, f2 = 0, f3 = 3, f5 = 5;
+ for (int i = 1; i < n; i++) {
+ int tmp = f2 < f3 ? f2 : f3, min = tmp < f5 ? tmp : f5;
+ ugly_nums[i] = min;
+ if (min == f2)
+ f2 = 2 * ugly_nums[++idx2];
+ if (min == f3)
+ f3 = 3 * ugly_nums[++idx3];
+ if (min == f5)
+ f5 = 5 * ugly_nums[++idx5];
+ }
+ int ans = ugly_nums[n - 1];
+ free(ugly_nums);
+ return ans;
+}
+
+int main() {
+ printf("%d\n", nthUglyNumber(10)); // expect: 12
+ printf("%d\n", nthUglyNumber(1)); // expect: 1
+}