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executable file
·70 lines (66 loc) · 1.56 KB
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/*
@filename subarraySum.cpp
@author caonan
@date 2022-04-12 15:21:15
@reference
@url https://leetcode-cn.com/problems/subarray-sum-equals-k/
@brief 给你一个整数数组 nums 和一个整数 k ，请你统计并返回 该数组中和为 k 的子数组的个数 。
*/
#include <assert.h>
#include <stdio.h>
#include <algorithm>
#include <iostream>
#include <map>
#include <unordered_map>
#include <vector>
using namespace std;
class Solution
{
public:
//暴力方法o(n^2)
int subarraySum(vector<int>& nums, int k)
{
int count = 0;
for (int i = 0; i < nums.size(); i++) {
int sum = 0;
for (int j = i; j < nums.size(); j++) {
sum += nums[j];
if (sum == k) {
count++;
}
}
}
return count;
}
};
class Solution1 : public Solution
{
public:
//前缀和
int subarraySum(vector<int>& nums, int k)
{
unordered_map<int, int> count_map;
int pre = 0;
int count = 0;
count_map[0] = 1;
for (int i = 0; i < nums.size(); i++) {
pre += nums[i];
if (count_map.find(pre - k) != count_map.end()) {
count += count_map[pre - k];
}
count_map[pre]++;
}
return count;
}
};
void uinttest(vector<int> arr, int k, int expect)
{
Solution s;
int ret = s.subarraySum(arr, k);
printf("expect %d,ret %d\n", expect, ret);
}
int main()
{
uinttest(vector<int>{1, 1, 1}, 2, 2);
return 0;
}