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	`1`	`+### 3672.Sum-of-Weighted-Modes-in-Subarrays`
	`2`	`+`
	`3`	`+比较容易想到设计两个容器:`
	`4`	+```cpp
	`5`	`+map<int,set<int>>freq2val;`
	`6`	`+unordered_map<int,int>val2freq;`
	`7`	+```
	`8`	+freq2val[f]里面放所有频率为f的元素(按照从小到大排序)。这样每个sliding window,我们就可以用`*(freq2val.rbegin()->second.begin())`找到其中的众数。val2[freq]顾名思义就是每种元素的频次。
	`9`	`+`
	`10`	`+每次我们加入一个新元素x,可以查到它的f。于是小心地更新这两个容器即可`
	`11`	+```cpp
	`12`	`+// 先删除{x,f}`
	`13`	`+freq2val[f].erase(x);`
	`14`	`+if (freq2val[f].empty())`
	`15`	`+ freq2val.erase(f);`
	`16`	`+// 再加入{x,f+1}`
	`17`	`+val2freq[x]=f+1;`
	`18`	`+freq2val[f+1].insert(x);`
	`19`	+```
	`20`	`+同理,每次我们删除一个旧元素x,可以查到它的f。也是小心地更新这两个容器即可`
	`21`	+```cpp
	`22`	`+// 先删除{x,f}`
	`23`	`+freq2val[f].erase(x);`
	`24`	`+if (freq2val[f].empty())`
	`25`	`+ freq2val.erase(f);`
	`26`	`+// 再加入{x,f+1}`
	`27`	`+val2freq[x] = f-1;`
	`28`	`+if (f!=1)`
	`29`	`+ freq2val[f-1].insert(x);`
	`30`	+```
	`31`	`+关键就是及时清理freq2val里没有值的key(即空频次),保证freq2val的结尾元素是有意义的。`

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