diff --git a/problems/0392.判断子序列.md b/problems/0392.判断子序列.md
index f7863c94..8d1a0208 100644
--- a/problems/0392.判断子序列.md
+++ b/problems/0392.判断子序列.md
@@ -221,21 +221,19 @@ function isSubsequence(s: string, t: string): boolean {
     /**
         dp[i][j]: s的前i-1个，t的前j-1个，最长公共子序列的长度
      */
-    const sLen: number = s.length,
-        tLen: number = t.length;
-    const dp: number[][] = new Array(sLen + 1).fill(0)
-        .map(_ => new Array(tLen + 1).fill(0));
+    const sLen = s.length
+    const tLen = t.length
+    const dp: number[][] = new Array(sLen + 1).fill(0).map(_ => new Array(tLen + 1).fill(0))
+
     for (let i = 1; i <= sLen; i++) {
         for (let j = 1; j <= tLen; j++) {
-            if (s[i - 1] === t[j - 1]) {
-                dp[i][j] = dp[i - 1][j - 1] + 1;
-            } else {
-                dp[i][j] = Math.max(dp[i - 1][j], dp[i][j - 1]);
-            }
+            if (s[i - 1] === t[j - 1]) dp[i][j] = dp[i - 1][j - 1] + 1
+            // 只需要取 j-2 的 dp 值即可，不用考虑 i-2
+            else dp[i][j] = dp[i][j - 1]
         }
     }
-    return dp[sLen][tLen] === s.length;
-};
+    return dp[sLen][tLen] === s.length
+}
 ```
 
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