upd

leetcode/weekly/397/a/README.md

@@ -32,11 +32,11 @@ class Solution {
 public:
     int findPermutationDifference(string s, string t) {
         int pos[26];
-        for (int i = 0; i < s.size(); i++) {
+        for (int i = 0; i < s.length(); i++) {
             pos[s[i] - 'a'] = i;
         }
         int ans = 0;
-        for (int i = 0; i < t.size(); i++) {
+        for (int i = 0; i < t.length(); i++) {
             ans += abs(i - pos[t[i] - 'a']);
         }
         return ans;
@@ -68,13 +68,20 @@ func abs(x int) int { if x < 0 { return -x }; return x }
 
 ## 分类题单
 
+[如何科学刷题？](https://leetcode.cn/circle/discuss/RvFUtj/)
+
 1. [滑动窗口（定长/不定长/多指针）](https://leetcode.cn/circle/discuss/0viNMK/)
 2. [二分算法（二分答案/最小化最大值/最大化最小值/第K小）](https://leetcode.cn/circle/discuss/SqopEo/)
-3. [单调栈（矩形系列/字典序最小/贡献法）](https://leetcode.cn/circle/discuss/9oZFK9/)
+3. [单调栈（基础/矩形面积/贡献法/最小字典序）](https://leetcode.cn/circle/discuss/9oZFK9/)
 4. [网格图（DFS/BFS/综合应用）](https://leetcode.cn/circle/discuss/YiXPXW/)
-5. [位运算（基础/性质/拆位/试填/恒等式/贪心/脑筋急转弯）](https://leetcode.cn/circle/discuss/dHn9Vk/)
+5. [位运算（基础/性质/拆位/试填/恒等式/思维）](https://leetcode.cn/circle/discuss/dHn9Vk/)
 6. [图论算法（DFS/BFS/拓扑排序/最短路/最小生成树/二分图/基环树/欧拉路径）](https://leetcode.cn/circle/discuss/01LUak/)
 7. [动态规划（入门/背包/状态机/划分/区间/状压/数位/数据结构优化/树形/博弈/概率期望）](https://leetcode.cn/circle/discuss/tXLS3i/)
 8. [常用数据结构（前缀和/差分/栈/队列/堆/字典树/并查集/树状数组/线段树）](https://leetcode.cn/circle/discuss/mOr1u6/)
+9. [数学算法（数论/组合/概率期望/博弈/计算几何/随机算法）](https://leetcode.cn/circle/discuss/IYT3ss/)
+10. [贪心算法（基本贪心策略/反悔/区间/字典序/数学/思维/脑筋急转弯/构造）](https://leetcode.cn/circle/discuss/g6KTKL/)
+11. [链表、二叉树与一般树（前后指针/快慢指针/DFS/BFS/直径/LCA）](https://leetcode.cn/circle/discuss/K0n2gO/)
 
 [我的题解精选（已分类）](https://github.com/EndlessCheng/codeforces-go/blob/master/leetcode/SOLUTIONS.md)
+
+欢迎关注 [B站@灵茶山艾府](https://space.bilibili.com/206214)