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Some notes on problems from SQL 50. https://leetcode.com/problems/consecutive-numbers/submissions/1431765550/?envType=study-plan-v2&envId=top-sql-50 SELECT l1.num AS ConsecutiveNums FROM Logs AS l1 JOIN Logs AS l2 JOIN Logs AS l3 WHERE l3.id - l2.id = 1 AND l2.id - l1.id = 1
玛利亚今年7岁 她迷上了名小男孩叫约翰 有一天玛利亚鼓起勇气向约翰发起了邀请 在公园一块玩儿 约翰也喜欢她 所以爽快答应了 约会当天她迫不及待的想见到约翰 回过神来她人已经在公园了 但是约翰还没到 她望着公园内盛开的姹紫嫣红的花儿们 没忍住摘了一朵花儿 想着一会儿献给自己最喜欢的约翰 没一会儿约翰如约到了公园 他见着玛利亚 招了招手 玛利亚也伸出手 只不过指尖捏着那朵刚摘下来的花 “我看这朵花很是漂亮 就摘下给你了 希望你会喜欢” 她脸红的跟桃子似的 “嗯 可是玛利亚 漂亮是漂亮 你这是在哪摘的” “就在这片草坪上”她手指向公园的土地上 “玛利亚 谢谢你的好意 我很感激 可是你 你摘鲜花献给我的行为是破坏环境的 ”约翰谴责了她 “十分抱歉 是我没有考虑过花儿的感受” “听好了玛利亚！花儿也是有生命的 你……以为这朵花儿漂亮你就能乱摘 那你就大错特错了”约翰越说越气愤“你这是在伤我的心！你个...你个破坏环境的臭杂种！” 见玛利亚掉下了眼泪 两眼都是悔意 约翰才住了嘴 玛利亚： “我对您的喜欢 就如同我摘下的这朵花儿一样
https://leetcode.com/problems/flip-equivalent-binary-trees/description/ This is a backtrace problem. We use recursion to check if all subtrees are Flip Equivalent. Steps: * determine the base cases * if both nodes are null, they are flip equivalent * if one node is null and the other is not null, not flip equiv
https://leetcode.com/problems/split-a-string-into-the-max-number-of-unique-substrings/description/?envType=daily-question&envId=2024-10-21 This is a backtrace problem. We check all possbile combinations, and find out the one with most unique substrings. Steps: * create a HashMap to store already used substrings * in the backtrack funtion, we select one substring, check if it
https://leetcode.com/problems/parsing-a-boolean-expression/?envType=daily-question&envId=2024-10-20 The intuition is to use stack. Then, the problem becomes when to do the operation on f and t, and how to do. Steps: * change epression to CharArray * initialize a stack * push each char into stack * if char is ), it
