diff --git a/066_plus_one/Makefile b/066_plus_one/Makefile
new file mode 100644
index 0000000..954c8bf
--- /dev/null
+++ b/066_plus_one/Makefile
@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test plus_one.c
diff --git a/066_plus_one/plus_one.c b/066_plus_one/plus_one.c
new file mode 100644
index 0000000..4f6005c
--- /dev/null
+++ b/066_plus_one/plus_one.c
@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/**
+ ** Return an array of size *returnSize.
+ ** Note: The returned array must be malloced, assume caller calls free().
+ **/
+static int* plusOne(int* digits, int digitsSize, int* returnSize)
+{
+    int i, j, len = 0, carry = 1;
+    int *result = malloc((digitsSize + 1) * sizeof(int));
+    for (i = digitsSize - 1; i >= 0 || carry; i--) {
+        int n = digits[i] + carry;
+        result[len++] = n % 10;
+        carry = n / 10;
+    }
+
+    for (i = 0, j = len - 1; i < j; i++, j--) {
+        int tmp = result[i];
+        result[i] = result[j];
+        result[j] = tmp;
+    }
+
+    *returnSize = len;
+    return result;
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 2) {
+        fprintf(stderr, "Usage: ./test num\n");
+        exit(-1);
+    }
+
+    int i, count = strlen(argv[1]);
+    int *digits = malloc(count * sizeof(int));
+    for (i = 0; i < count; i++) {
+        digits[i] = argv[1][i] - '0';
+    }
+
+    int len = 0;
+    int *res = plusOne(digits, count, &len);
+    for (i = 0; i < len; i++) {
+        printf("%c", res[i] + '0');
+    }
+    printf("\n");
+    return 0;
+}
diff --git a/067_add_binary/Makefile b/067_add_binary/Makefile
new file mode 100644
index 0000000..5b996ad
--- /dev/null
+++ b/067_add_binary/Makefile
@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test add_binary.c
diff --git a/067_add_binary/add_binary.c b/067_add_binary/add_binary.c
new file mode 100644
index 0000000..3eef3d9
--- /dev/null
+++ b/067_add_binary/add_binary.c
@@ -0,0 +1,40 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static char* addBinary(char* a, char* b)
+{
+    int len1 = strlen(a);
+    int len2 = strlen(b);
+    int len = len1 > len2 ? len1 + 1 : len2 + 1;
+    char *result = malloc(len + 1);
+    result[len] = '\0';
+    result[len - 1] = '\0';
+
+    int i, j, carry = 0;
+    len = 0;
+    for (i = len1 - 1, j = len2 - 1; carry || i >= 0 || j >= 0; i--, j--) {
+        int na = i >= 0 ? a[i] - '0' : 0;
+        int nb = j >= 0 ? b[j] - '0' : 0;
+        result[len++] = (na ^ nb ^ carry) + '0';
+        carry = carry + na + nb >= 2 ? 1 : 0;
+    }
+
+    for (i = 0, j = len - 1; i < j; i++, j--) {
+        char c = result[i];
+        result[i] = result[j];
+        result[j] = c;
+    }
+
+    return result;
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 3) {
+        fprintf(stderr, "Usage: ./test s1 s2\n");
+        exit(-1);
+    }
+    printf("%s\n", addBinary(argv[1], argv[2]));
+    return 0;
+}