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Commitea31c7b

Browse files
refactor 560
1 parente5f030b commitea31c7b

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2 files changed

+27
-22
lines changed

2 files changed

+27
-22
lines changed

‎src/main/java/com/fishercoder/solutions/_560.java

Lines changed: 24 additions & 19 deletions
Original file line numberDiff line numberDiff line change
@@ -17,27 +17,32 @@
1717
*/
1818
publicclass_560 {
1919

20-
/**credit: https://discuss.leetcode.com/topic/87850/java-solution-presum-hashmap
21-
* We know the key to solve this problem is SUM[i, j].
22-
* So if we know SUM[0, i - 1] and SUM[0, j],
23-
* then we can easily get SUM[i, j] via (SUM[0, j] - SUM[0, i-1]).
24-
* To achieve this, we just need to go through the array,
25-
* calculate the current sum and save number of all seen PreSum to a HashMap.
26-
*
27-
* Time complexity O(n), Space complexity O(n).*/
28-
publicintsubarraySum(int[]nums,intk) {
29-
Map<Integer,Integer>preSum =newHashMap();
30-
intsum =0;
31-
intresult =0;
32-
preSum.put(0,1);
33-
for (inti =0;i <nums.length;i++) {
34-
sum +=nums[i];
35-
if (preSum.containsKey(sum -k)) {
36-
result +=preSum.get(sum -k);
20+
publicstaticclassSolution1 {
21+
22+
/**
23+
* credit: https://discuss.leetcode.com/topic/87850/java-solution-presum-hashmap
24+
* We know the key to solve this problem is SUM[i, j].
25+
* So if we know SUM[0, i - 1] and SUM[0, j],
26+
* then we can easily get SUM[i, j] via (SUM[0, j] - SUM[0, i-1]).
27+
* To achieve this, we just need to go through the array,
28+
* calculate the current sum and save number of all seen PreSum to a HashMap.
29+
* <p>
30+
* Time complexity O(n), Space complexity O(n).
31+
*/
32+
publicintsubarraySum(int[]nums,intk) {
33+
Map<Integer,Integer>preSum =newHashMap();
34+
intsum =0;
35+
intresult =0;
36+
preSum.put(0,1);
37+
for (inti =0;i <nums.length;i++) {
38+
sum +=nums[i];
39+
if (preSum.containsKey(sum -k)) {
40+
result +=preSum.get(sum -k);
41+
}
42+
preSum.put(sum,preSum.getOrDefault(sum,0) +1);
3743
}
38-
preSum.put(sum,preSum.getOrDefault(sum,0) +1);
44+
returnresult;
3945
}
40-
returnresult;
4146
}
4247

4348
}

‎src/test/java/com/fishercoder/_560Test.java

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -10,23 +10,23 @@
1010
* Created by fishercoder on 4/29/17.
1111
*/
1212
publicclass_560Test {
13-
privatestatic_560test;
13+
privatestatic_560.Solution1solution1;
1414
privatestaticintexpected;
1515
privatestaticintactual;
1616
privatestaticint[]nums;
1717
privatestaticintk;
1818

1919
@BeforeClass
2020
publicstaticvoidsetup() {
21-
test =new_560();
21+
solution1 =new_560.Solution1();
2222
}
2323

2424
@Test
2525
publicvoidtest1() {
2626
nums =newint[]{1,1,1};
2727
k =2;
2828
expected =2;
29-
actual =test.subarraySum(nums,k);
29+
actual =solution1.subarraySum(nums,k);
3030
assertEquals(expected,actual);
3131
}
3232
}

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