leetcode 87

leetcode/87/87.go

@@ -0,0 +1,68 @@
+func isScramble(s1, s2 string) bool {
+    n1 := len(s1)
+    n2 := len(s2)
+    if n1 != n2 {
+        return false
+    }
+
+    dp := make([][][]int8, n1)
+    for i := 0; i < n1; i++ {
+        dp[i] = make([][]int8, n2)
+        for j := 0; j < n2; j++ {
+            dp[i][j] = make([]int8, n1 - i + 1)
+            for k := 0; k < n1 - i + 1; k++ {
+                dp[i][j][k] = -1
+            }
+        }
+    }
+
+    count := [26]int{}
+    
+    var check func(i1, i2, l int) int8
+    check = func(i1, i2, l int) int8 {
+        if dp[i1][i2][l] == -1 {
+            // 字符相同
+            x, y := s1[i1:i1+l], s2[i2:i2+l]
+            if x == y {
+                dp[i1][i2][l] = 1
+            } 
+
+            if dp[i1][i2][l] == -1 {
+                // 字符频率不同
+                for i := 0; i < 26; i++ {
+                    count[i] = 0
+                }
+                for i, ch := range x {
+                    count[ch-'a']++
+                    count[y[i]-'a']--
+                }
+                for _, f := range count[:] {
+                    if f != 0 {
+                        dp[i1][i2][l] = 0
+                    }
+                }
+            }
+
+            if dp[i1][i2][l] == -1 {
+                // 枚举分割位置
+                for i := 1; i < l; i++ {
+                    // 不交换的情况
+                    if check(i1, i2, i) == 1 && check(i1+i, i2+i, l-i) == 1 {
+                        dp[i1][i2][l] = 1
+                    }
+                    // 交换的情况
+                    if check(i1, i2+l-i, i) == 1 && check(i1+i, i2, l-i) == 1 {
+                        dp[i1][i2][l] = 1
+                    }
+                }
+            }
+
+            if dp[i1][i2][l] == -1 {
+                // 检查失败,无法转移
+                dp[i1][i2][l] = 0
+            }
+        }
+        return dp[i1][i2][l]
+    }
+    return check(0, 0, n1) == 1
+}