Improve

Signed-off-by: Leo Ma <begeekmyfriend@gmail.com>

Author: begeekmyfriend

202_happy_number/Makefile

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test happy_number.c

202_happy_number/happy_number.c

@@ -0,0 +1,37 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+
+static bool recursive(int n, bool *used, const int *sq)
+{
+    if (n == 1) return true;
+    if (n < 10000) {
+        if (used[n]) return false;
+        used[n] = true;
+    }
+    int sum = 0;
+    while (n > 0) {
+        sum += sq[n % 10];
+        n /= 10;
+    }
+    return recursive(sum, used, sq);
+}
+
+static bool isHappy(int n)
+{
+    bool used[10000] = { false };
+    const static int sq[10] = { 0, 1, 4, 9, 16, 25, 36, 49, 64, 81 };
+    return recursive(n, used, sq);
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 2) {
+        fprintf(stderr, "Usage: ./test n\n");
+        exit(-1);
+    }
+
+    printf("%s\n", isHappy(atoi(argv[1])) ? "true" : "false");
+    return 0;
+}

203_remove_linked_list_element/Makefile

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test rm_elem.c

203_remove_linked_list_element/rm_elem.c

@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+struct ListNode {
+    int val;
+    struct ListNode *next;
+};
+
+static struct ListNode *removeElement(struct ListNode *head, int val)
+{
+    struct ListNode dummy;
+    dummy.next = head;
+    struct ListNode *prev = &dummy;
+    struct ListNode *p = head;
+    while (p != NULL) {
+        if (p->val == val) {
+            prev->next = p->next;
+        } else {
+            prev = p;
+        }
+        p = p->next;
+    }
+    return dummy.next;
+}
+
+int main(int argc, char **argv)
+{
+    if (argc < 3) {
+        fprintf(stderr, "Usage: ./test value n1 n2 n3...\n");
+        exit(-1);
+    }
+
+    int value = atoi(argv[1]);
+    int i, count = argc - 2;
+    struct ListNode *head = NULL, *p, *prev;
+    for (i = 0; i < count; i++) {
+        p = malloc(sizeof(*p));
+        p->val = atoi(argv[i + 2]);
+        p->next = NULL;
+        if (head == NULL) {
+            head = p;
+        } else {
+            prev->next = p;
+        }
+        prev = p;
+    }
+
+    for (p = removeElement(head, value); p != NULL; p = p->next) {
+        printf("%d ", p->val);
+    }
+    printf("\n");
+    return 0;
+}

204_count_primes/Makefile

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test count_primes.c

204_count_primes/count_primes.c

@@ -0,0 +1,37 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+
+static int countPrimes(int n)
+{
+    if (n < 3) return 0;
+    
+    int i, j;
+    bool *marked = malloc(n);
+    memset(marked, false, n);
+    int count = n >> 1;
+
+    for (i = 3; i * i <= n; i += 2) {
+        if (!marked[i]) {
+            for (j = i * i; j < n; j += (i << 1)) {
+                if (!marked[j]) {
+                    marked[j] = true;
+                    --count;
+                }
+            }
+        }
+    }
+    return count;
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 2) {
+        fprintf(stderr, "Usage: ./test n\n");
+        exit(-1);
+    }
+
+    printf("%d\n", countPrimes(atoi(argv[1])));
+    return 0;
+}

205_isomorphic_strings/1

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test isomorphic_strings.c

205_isomorphic_strings/Makefile

@@ -0,0 +1,32 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+static bool isIsomorphic(char *s, char *t)
+{
+    int i;
+    char smap[128] = { '\0' };
+    char tmap[128] = { '\0' };
+    while (*s != '\0' && *t != '\0') {
+        if ((smap[*s] != '\0' && smap[*s] != *t) ||
+            (tmap[*t] != '\0' && tmap[*t] != *s)) {
+            return false;
+        }
+        smap[*s] = *t;
+        tmap[*t] = *s;
+        s++;
+        t++;
+    }
+    return *s == *t;
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 3) {
+        fprintf(stderr, "Usage: ./test s1 s2\n");
+        exit(-1);
+    }
+
+    printf("%s\n", isIsomorphic(argv[1], argv[2]) ? "true" : "false");
+    return 0;
+}

205_isomorphic_strings/isomorphic_strings.c

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test reverse_list.c