Decode ways

Signed-off-by: Leo Ma <[email protected]>

091_decode_ways/Makefile

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

091_decode_ways/decode_ways.c

@@ -0,0 +1,70 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+//static void recursive(char *s, char *stack, int len, char **results, int *count)
+//{
+//    if (*s == '\0') {
+//        printf("%s\n", stack);
+//        results[*count] = malloc(len + 1);
+//        strcpy(results[*count], stack);
+//        (*count)++;
+//    } else {
+//        //while (*s != '\0') {
+//            stack[len++] = *s - '0' - 1 + 'A';
+//            recursive(s + 1, stack, len, results, count);
+//            stack[--len] = '\0';
+//            if (*(s + 1) != '\0') {
+//                int value = (*s - '0') * 10 + (*(s + 1) - '0');
+//                char c = (value - 1) + 'A';
+//                if (c >= 'A' && c <= 'Z') {
+//                    stack[len++] = c;
+//                    recursive(s + 2, stack, len, results, count);
+//                    stack[--len] = '\0';
+//                    //s++;
+//                }
+//            }
+//            //s++;
+//        //}
+//    }
+//}
+
+static void recursive(char *s, int *count)
+{
+    int value;
+    char c;
+    if (*s == '\0') {
+        (*count)++;
+    } else {
+        value = *s - '0';
+        c = (value - 1) + 'A';
+        if (c >= 'A' && c <= 'Z') {
+            recursive(s + 1, count);
+        }
+        if (*(s + 1) != '\0' && *s != '0') {
+            value = (*s - '0') * 10 + (*(s + 1) - '0');
+            c = (value - 1) + 'A';
+            if (c >= 'A' && c <= 'Z') {
+                recursive(s + 2, count);
+            }
+        }
+    }
+}
+
+static int numDecodings(char* s) {
+    int count = 0;
+    if (*s != '\0' && *s != '0') {
+        recursive(s, &count);
+    }
+    return count;
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 2) {
+        fprintf(stderr, "Usage: ./test number\n");
+        exit(-1);
+    }
+    printf("%d\n", numDecodings(argv[1]));
+    return 0;
+}