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feat: add solutions to lcof2 problems: No.035,039 (#1403)
* No.035.最小时间差 * No.039.直方图最大矩形面积
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‎lcof2/剑指 Offer II 035. 最小时间差/README.md

Lines changed: 44 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -39,16 +39,18 @@
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<!-- 这里可写通用的实现逻辑 -->
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42-
我们注意到，时间点最多只有 `24 * 60` 个，因此，当 timePoints 长度超过 `24 * 60`，说明有重复的时间点，提前返回 0。
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**方法一：排序**
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44-
接下来：
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我们注意到，时间点最多只有 $24 \times 60$ 个，因此，当 $timePoints$ 长度超过 $24 \times 60$，说明有重复的时间点，提前返回 $0$。
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首先，遍历时间列表，将其转换为“分钟制”列表 `mins`，比如，对于时间点 `13:14`，将其转换为 `13 * 60 + 14`。
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接下来，我们首先遍历时间列表，将其转换为“分钟制”列表 $mins$，比如，对于时间点 `13:14`，将其转换为 $13 \times 60 + 14$。
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48-
接着将“分钟制”列表按升序排列，然后将此列表的最小时间 `mins[0]` 加上 `24 * 60` 追加至列表尾部，用于处理最大值、最小值的差值这种特殊情况。
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接着将“分钟制”列表按升序排列，然后将此列表的最小时间 $mins[0]$ 加上 $24 \times 60$ 追加至列表尾部，用于处理最大值、最小值的差值这种特殊情况。
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最后遍历“分钟制”列表，找出相邻两个时间的最小值即可。
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时间复杂度 $O(n \times \log n)$，空间复杂度 $O(n)$。其中 $n$ 为时间点个数。
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<!-- tabs:start -->
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### **Python3**
@@ -62,10 +64,7 @@ class Solution:
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return 0
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mins = sorted(int(t[:2]) * 60 + int(t[3:]) for t in timePoints)
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mins.append(mins[0] + 24 * 60)
65-
res = mins[-1]
66-
for i in range(1, len(mins)):
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res = min(res, mins[i] - mins[i - 1])
68-
return res
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return min(b - a for a, b in pairwise(mins))
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```
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### **Java**
@@ -85,11 +84,11 @@ class Solution {
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}
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Collections.sort(mins);
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mins.add(mins.get(0) + 24 * 60);
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int res = 24 * 60;
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int ans = 1 << 30;
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for (int i = 1; i < mins.size(); ++i) {
90-
res = Math.min(res, mins.get(i) - mins.get(i - 1));
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ans = Math.min(ans, mins.get(i) - mins.get(i - 1));
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}
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return res;
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return ans;
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}
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}
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```
@@ -100,17 +99,20 @@ class Solution {
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class Solution {
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public:
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int findMinDifference(vector<string>& timePoints) {
103-
if (timePoints.size() > 24 * 60)
102+
if (timePoints.size() > 24 * 60) {
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return 0;
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}
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vector<int> mins;
106-
for (auto t : timePoints)
106+
for (auto& t : timePoints) {
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mins.push_back(stoi(t.substr(0, 2)) * 60 + stoi(t.substr(3)));
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}
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sort(mins.begin(), mins.end());
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mins.push_back(mins[0] + 24 * 60);
110-
int res = 24 * 60;
111-
for (int i = 1; i < mins.size(); ++i)
112-
res = min(res, mins[i] - mins[i - 1]);
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return res;
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int ans = 1 << 30;
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for (int i = 1; i < mins.size(); ++i) {
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ans = min(ans, mins[i] - mins[i - 1]);
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}
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return ans;
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}
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};
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```
@@ -131,11 +133,11 @@ func findMinDifference(timePoints []string) int {
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}
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sort.Ints(mins)
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mins = append(mins, mins[0]+24*60)
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res := 24 * 60
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for i := 1; i < len(mins); i++ {
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res = min(res, mins[i]-mins[i-1])
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ans := 1 << 30
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for i, x := range mins[1:] {
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ans = min(ans, x-mins[i])
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}
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return res
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return ans
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}
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func min(a, b int) int {
@@ -146,6 +148,27 @@ func min(a, b int) int {
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}
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```
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### **TypeScript**
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```ts
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function findMinDifference(timePoints: string[]): number {
155+
if (timePoints.length > 24 * 60) {
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return 0;
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}
158+
const mins: number[] = timePoints.map(timePoint => {
159+
const [hour, minute] = timePoint.split(':').map(num => parseInt(num));
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return hour * 60 + minute;
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});
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mins.sort((a, b) => a - b);
163+
mins.push(mins[0] + 24 * 60);
164+
let ans = 1 << 30;
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for (let i = 1; i < mins.length; ++i) {
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ans = Math.min(ans, mins[i] - mins[i - 1]);
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}
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return ans;
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}
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```
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### **...**
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```

‎lcof2/剑指 Offer II 035. 最小时间差/Solution.cpp

Lines changed: 18 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -1,16 +1,19 @@
1-
class Solution {
2-
public:
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int findMinDifference(vector<string>& timePoints) {
4-
if (timePoints.size() > 24 * 60)
5-
return 0;
6-
vector<int> mins;
7-
for (auto t : timePoints)
8-
mins.push_back(stoi(t.substr(0, 2)) * 60 + stoi(t.substr(3)));
9-
sort(mins.begin(), mins.end());
10-
mins.push_back(mins[0] + 24 * 60);
11-
int res = 24 * 60;
12-
for (int i = 1; i < mins.size(); ++i)
13-
res = min(res, mins[i] - mins[i - 1]);
14-
return res;
15-
}
1+
class Solution {
2+
public:
3+
int findMinDifference(vector<string>& timePoints) {
4+
if (timePoints.size() > 24 * 60) {
5+
return 0;
6+
}
7+
vector<int> mins;
8+
for (auto& t : timePoints) {
9+
mins.push_back(stoi(t.substr(0, 2)) * 60 + stoi(t.substr(3)));
10+
}
11+
sort(mins.begin(), mins.end());
12+
mins.push_back(mins[0] + 24 * 60);
13+
int ans = 1 << 30;
14+
for (int i = 1; i < mins.size(); ++i) {
15+
ans = min(ans, mins[i] - mins[i - 1]);
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}
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return ans;
18+
}
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};

‎lcof2/剑指 Offer II 035. 最小时间差/Solution.go

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -11,11 +11,11 @@ func findMinDifference(timePoints []string) int {
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}
1212
sort.Ints(mins)
1313
mins = append(mins, mins[0]+24*60)
14-
res := 24 * 60
15-
for i := 1; i < len(mins); i++ {
16-
res = min(res, mins[i]-mins[i-1])
14+
ans := 1 << 30
15+
for i, x := range mins[1:] {
16+
ans = min(ans, x-mins[i])
1717
}
18-
return res
18+
return ans
1919
}
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2121
func min(a, b int) int {

‎lcof2/剑指 Offer II 035. 最小时间差/Solution.java

Lines changed: 18 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -1,19 +1,19 @@
1-
class Solution {
2-
public int findMinDifference(List<String> timePoints) {
3-
if (timePoints.size() > 24 * 60) {
4-
return 0;
5-
}
6-
List<Integer> mins = new ArrayList<>();
7-
for (String t : timePoints) {
8-
String[] time = t.split(":");
9-
mins.add(Integer.parseInt(time[0]) * 60 + Integer.parseInt(time[1]));
10-
}
11-
Collections.sort(mins);
12-
mins.add(mins.get(0) + 24 * 60);
13-
int res = 24 * 60;
14-
for (int i = 1; i < mins.size(); ++i) {
15-
res = Math.min(res, mins.get(i) - mins.get(i - 1));
16-
}
17-
return res;
18-
}
1+
class Solution {
2+
public int findMinDifference(List<String> timePoints) {
3+
if (timePoints.size() > 24 * 60) {
4+
return 0;
5+
}
6+
List<Integer> mins = new ArrayList<>();
7+
for (String t : timePoints) {
8+
String[] time = t.split(":");
9+
mins.add(Integer.parseInt(time[0]) * 60 + Integer.parseInt(time[1]));
10+
}
11+
Collections.sort(mins);
12+
mins.add(mins.get(0) + 24 * 60);
13+
int ans = 1 << 30;
14+
for (int i = 1; i < mins.size(); ++i) {
15+
ans = Math.min(ans, mins.get(i) - mins.get(i - 1));
16+
}
17+
return ans;
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}
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}

‎lcof2/剑指 Offer II 035. 最小时间差/Solution.py

Lines changed: 7 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -1,10 +1,7 @@
1-
class Solution:
2-
def findMinDifference(self, timePoints: List[str]) -> int:
3-
if len(timePoints) > 24 * 60:
4-
return 0
5-
mins = sorted(int(t[:2]) * 60 + int(t[3:]) for t in timePoints)
6-
mins.append(mins[0] + 24 * 60)
7-
res = mins[-1]
8-
for i in range(1, len(mins)):
9-
res = min(res, mins[i] - mins[i - 1])
10-
return res
1+
class Solution:
2+
def findMinDifference(self, timePoints: List[str]) -> int:
3+
if len(timePoints) > 24 * 60:
4+
return 0
5+
mins = sorted(int(t[:2]) * 60 + int(t[3:]) for t in timePoints)
6+
mins.append(mins[0] + 24 * 60)
7+
return min(b - a for a, b in pairwise(mins))

‎lcof2/剑指 Offer II 035. 最小时间差/Solution.ts

Lines changed: 16 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,16 @@
1+
function findMinDifference(timePoints: string[]): number {
2+
if (timePoints.length > 24 * 60) {
3+
return 0;
4+
}
5+
const mins: number[] = timePoints.map(timePoint => {
6+
const [hour, minute] = timePoint.split(':').map(num => parseInt(num));
7+
return hour * 60 + minute;
8+
});
9+
mins.sort((a, b) => a - b);
10+
mins.push(mins[0] + 24 * 60);
11+
let ans = 1 << 30;
12+
for (let i = 1; i < mins.length; ++i) {
13+
ans = Math.min(ans, mins[i] - mins[i - 1]);
14+
}
15+
return ans;
16+
}

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