From ed37657c6cf6bf6e0b1b9a44b109b280c33f2424 Mon Sep 17 00:00:00 2001
From: Leo Ma <begeekmyfriend@gmail.com>
Date: Sun, 3 Sep 2017 10:17:11 +0800
Subject: [PATCH] Scramble string

Signed-off-by: Leo Ma <begeekmyfriend@gmail.com>
---
 087_scramble_string/Makefile          |  2 +
 087_scramble_string/scramble_string.c | 66 +++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)
 create mode 100644 087_scramble_string/Makefile
 create mode 100644 087_scramble_string/scramble_string.c

diff --git a/087_scramble_string/Makefile b/087_scramble_string/Makefile
new file mode 100644
index 0000000..52cecd7
--- /dev/null
+++ b/087_scramble_string/Makefile
@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test scramble_string.c
diff --git a/087_scramble_string/scramble_string.c b/087_scramble_string/scramble_string.c
new file mode 100644
index 0000000..1eb5c8a
--- /dev/null
+++ b/087_scramble_string/scramble_string.c
@@ -0,0 +1,66 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+
+/* The recursive way is quite simple.
+ *    1) break the string to two parts: 
+ *          s1[0..j]   s1[j+1..n]
+ *          s2[0..j]   s2[j+1..n]
+ *    2) then
+ *          isScramble(s1[0..j], s2[0..j]) &&  isScramble(s1[j+1..n], s2[j+1..n])
+ *       or
+ *          isScramble(s1[0..j], s2[n - j - 1, n]) &&  isScramble(s1[j+1..n], s2[0..n - j])
+ */
+#define N 128
+
+static bool scramble(char *s1, int low1, int high1, char *s2, int low2, int high2)
+{
+    if (high1 - low1 != high2 - low2) {
+        return false;
+    } else if (!memcmp(s1 + low1, s2 + low2, high1 - low1 + 1)) {
+        return true;
+    } else {
+        int i, c1[N], c2[N];
+        memset(c1, 0, N * sizeof(int));
+        memset(c2, 0, N * sizeof(int));
+        for (i = low1; i <= high1; i++) {
+            c1[s1[i]]++;
+        }
+        for (i = low2; i <= high2; i++) {
+            c2[s2[i]]++;
+        }
+        if (memcmp(c1, c2, N * sizeof(int))) {
+            return false;
+        } else {
+            int len = high1 - low1 + 1;
+            for (i = 1; i < len; i++) {
+                if (scramble(s1, low1, low1 + i - 1, s2, low2, low2 + i - 1) &&
+                    scramble(s1, low1 + i, high1, s2, low2 + i, high2)) {
+                    return true;
+                }
+                if (scramble(s1, low1, low1 + i - 1, s2, high2 - i + 1, high2) &&
+                    scramble(s1, low1 + i, high1, s2, low2, high2 - i)) {
+                    return true;
+                }
+            }
+            return false;
+        }
+    }
+}
+
+static bool isScramble(char* s1, char* s2) {
+    int len1 = strlen(s1);
+    int len2 = strlen(s2);
+    return scramble(s1, 0, len1 - 1, s2, 0, len2 - 1);
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 3) {
+        fprintf(stderr, "Usage: ./test s1 s2\n");
+        exit(-1);
+    }
+    printf("%s\n", isScramble(argv[1], argv[2]) ? "true" : "false");
+    return 0;
+}