139.ts dp 迭代写法

Author: gongtao02

139.ts

@@ -6,27 +6,49 @@
 
 // @lc code=start
 /**
- * 
+ * 解法 1： 自顶向下
+ */
+// function wordBreak(s: string, wordDict: string[]): boolean {
+//   const dpTable = new Map()
+//   function dp(s) {
+//     if (s === '') return true
+//     if (dpTable.has(s)) return dpTable.get(s)
+//     for (let i = 0; i < wordDict.length; i++) {
+//       let result = dp(s.substring(wordDict[i].length))
+//       dpTable.set(s.substring(wordDict[i].length), result)
+//       if (s.substring(0, wordDict[i].length) === wordDict[i] && result) {
+//         return true
+//       }
+//     }
+//     return false
+//   }
+//   return dp(s)
+// };
+
+/**
+ * 解法 2： 自底向上
  */
 function wordBreak(s: string, wordDict: string[]): boolean {
-  const dpTable = new Map()
-  function dp(s) {
-    if (s === '') return true
-    if (dpTable.has(s)) return dpTable.get(s)
-    for (let i = 0; i < wordDict.length; i++) {
-      let result = dp(s.substring(wordDict[i].length))
-      dpTable.set(s.substring(wordDict[i].length), result)
-      if (s.substring(0, wordDict[i].length) === wordDict[i] && result) {
-        return true
+
+  // 空字符串，可以组合成
+  // const dp = [true]
+  const dpMap = new Map()
+  dpMap.set('', true)
+  for (let i = 0; i < s.length; i++) {
+    for (let j = 0; j < wordDict.length; j++) {
+      if (dpMap.get(s.substring(0, i)) && s.substring(i, i + wordDict[j].length) === wordDict[j]) {
+        dpMap.set(s.substring(0, i) + wordDict[j], true)
+        // break
       }
+
     }
-    return false
   }
-  return dp(s)
-};
+  return !!dpMap.get(s)
+}
+
 // @lc code=end
 
-// console.log(wordBreak("leetcode", ["leet", "code"]))
-console.log(wordBreak("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaab", 
-  ["a", "aa", "aaa", "aaaa", "aaaaa", "aaaaaa", "aaaaaaa", "aaaaaaaa", "aaaaaaaaa", "aaaaaaaaaa"]))
+console.log(wordBreak("applepenapple", ["apple", "pen"]))
+// console.log(wordBreak("aab",
+//   ["a", "aa", "aaa", "aaaa", "aaaaa", "aaaaaa", "aaaaaaa", "aaaaaaaa", "aaaaaaaaa", "aaaaaaaaaa"]))