Commit 545e87d

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Add new problem

Signed-off-by: begeekmyfriend <begeekmyfriend@gmail.com>

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	`1`	`+#include <bits/stdc++.h>`
	`2`	`+`
	`3`	`+using namespace std;`
	`4`	`+`
	`5`	`+class Solution {`
	`6`	`+public:`
	`7`	`+ int subarraySum(vector<int>& nums, int k) {`
	`8`	`+ int res = 0, sum = 0;`
	`9`	`+ unordered_map<int, int> pre_sum_cnt;`
	`10`	`+`
	`11`	`+ // The prefix sum array records the sum of nums[0...i], so we have`
	`12`	`+ // presum[j] - presum[j] = k when the sum of nums[i...j] equals k.`
	`13`	`+ // The presum[0] should always be 0. And pre_sum_cnt[0] = 1.`
	`14`	`+ pre_sum_cnt[0] = 1;`
	`15`	`+ for (const auto n : nums) {`
	`16`	`+ // Here the sum means sum of nums[0...j] and the sum0 means sum`
	`17`	`+ // of nums[0...i] then there will be sum - sum0 = k.`
	`18`	`+ sum += n;`
	`19`	`+ int sum0 = sum - k;`
	`20`	`+ if (ht.count(sum0)) {`
	`21`	`+ res += pre_sum_cnt[sum0];`
	`22`	`+ }`
	`23`	`+ pre_sum_cnt[sum]++;`
	`24`	`+ }`
	`25`	`+`
	`26`	`+ return res;`
	`27`	`+ }`
	`28`	`+};`

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