|
51 | 51 |
|
52 | 52 | <!-- 这里可写通用的实现逻辑 -->
|
53 | 53 |
|
| 54 | +**方法一:记忆化搜索 + 二分查找** |
| 55 | + |
| 56 | +我们先将 `rides` 按照 `start` 从小到大排序,然后设计一个函数 $dfs(i)$,表示从第 $i$ 个乘客开始接单,最多能获得的小费。答案即为 $dfs(0)$。 |
| 57 | + |
| 58 | +函数 $dfs(i)$ 的计算过程如下: |
| 59 | + |
| 60 | +对于第 $i$ 个乘客,我们可以选择接单,也可以选择不接单。如果不接单,那么最多能获得的小费为 $dfs(i + 1)$;如果接单,那么我们可以通过二分查找,找到在第 $i$ 个乘客下车地点之后遇到的第一个乘客,记为 $j$,那么最多能获得的小费为 $dfs(j) + end_i - start_i + tip_i$。取两者的较大值即可。即: |
| 61 | + |
| 62 | +$$ |
| 63 | +dfs(i) = \max(dfs(i + 1), dfs(j) + end_i - start_i + tip_i) |
| 64 | +$$ |
| 65 | + |
| 66 | +其中 $j$ 是满足 $start_j \ge end_i$ 的最小的下标,可以通过二分查找得到。 |
| 67 | + |
| 68 | +此过程中,我们可以使用记忆化搜索,将每个状态的答案保存下来,避免重复计算。 |
| 69 | + |
| 70 | +时间复杂度 $O(m\times \log m)$,其中 $m$ 为 `rides` 的长度。 |
| 71 | + |
| 72 | +**方法二:动态规划 + 二分查找** |
| 73 | + |
| 74 | +我们可以将方法一中的记忆化搜索改为动态规划。 |
| 75 | + |
| 76 | +先将 `rides` 排序,这次我们按照 `end` 从小到大排序。然后定义 $dp[i]$,表示前 $i$ 个乘客中,最多能获得的小费。答案即为 $dp[m]$。初始化 $dp[0] = 0$。 |
| 77 | + |
| 78 | +对于第 $i$ 个乘客,我们可以选择接单,也可以选择不接单。如果不接单,那么最多能获得的小费为 $dp[i]$;如果接单,我们可以通过二分查找,找到在第 $i$ 个乘客上车地点之前,最后一个下车地点不大于 $start_i$ 的乘客,记为 $j$,那么最多能获得的小费为 $dp[j] + end_i - start_i + tip_i$。取两者的较大值即可。即: |
| 79 | + |
| 80 | +$$ |
| 81 | +dp[i] = \max(dp[i - 1], dp[j] + end_i - start_i + tip_i) |
| 82 | +$$ |
| 83 | + |
| 84 | +其中 $j$ 是满足 $end_j \le start_i$ 的最大的下标,可以通过二分查找得到。 |
| 85 | + |
| 86 | +时间复杂度 $O(m\times \log m)$,其中 $m$ 为 `rides` 的长度。 |
| 87 | + |
| 88 | +相似题目: |
| 89 | + |
| 90 | +- [1235. 规划兼职工作](/solution/1200-1299/1235.Maximum%20Profit%20in%20Job%20Scheduling/README.md) |
| 91 | +- [1751. 最多可以参加的会议数目 II](/solution/1700-1799/1751.Maximum%20Number%20of%20Events%20That%20Can%20Be%20Attended%20II/README.md) |
| 92 | + |
54 | 93 | <!-- tabs:start -->
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55 | 94 |
|
56 | 95 | ### **Python3**
|
57 | 96 |
|
58 | 97 | <!-- 这里可写当前语言的特殊实现逻辑 -->
|
59 | 98 |
|
60 | 99 | ```python
|
| 100 | +class Solution: |
| 101 | + def maxTaxiEarnings(self, n: int, rides: List[List[int]]) -> int: |
| 102 | + @cache |
| 103 | + def dfs(i): |
| 104 | + if i >= len(rides): |
| 105 | + return 0 |
| 106 | + s, e, t = rides[i] |
| 107 | + j = bisect_left(rides, e, lo=i + 1, key=lambda x: x[0]) |
| 108 | + return max(dfs(i + 1), dfs(j) + e - s + t) |
61 | 109 |
|
| 110 | + rides.sort() |
| 111 | + return dfs(0) |
| 112 | +``` |
| 113 | + |
| 114 | +```python |
| 115 | +class Solution: |
| 116 | + def maxTaxiEarnings(self, n: int, rides: List[List[int]]) -> int: |
| 117 | + rides.sort(key=lambda x: x[1]) |
| 118 | + m = len(rides) |
| 119 | + dp = [0] * (m + 1) |
| 120 | + for i, (s, e, t) in enumerate(rides): |
| 121 | + j = bisect_right(rides, s, hi=i, key=lambda x: x[1]) |
| 122 | + dp[i + 1] = max(dp[i], dp[j] + e - s + t) |
| 123 | + return dp[m] |
62 | 124 | ```
|
63 | 125 |
|
64 | 126 | ### **Java**
|
65 | 127 |
|
66 | 128 | <!-- 这里可写当前语言的特殊实现逻辑 -->
|
67 | 129 |
|
68 | 130 | ```java
|
| 131 | +class Solution { |
| 132 | + private int[][] rides; |
| 133 | + private long[] f; |
| 134 | + private int m; |
| 135 | + |
| 136 | + public long maxTaxiEarnings(int n, int[][] rides) { |
| 137 | + m = rides.length; |
| 138 | + f = new long[m]; |
| 139 | + Arrays.sort(rides, (a, b) -> a[0] - b[0]); |
| 140 | + this.rides = rides; |
| 141 | + return dfs(0); |
| 142 | + } |
| 143 | + |
| 144 | + private long dfs(int i) { |
| 145 | + if (i >= m) { |
| 146 | + return 0; |
| 147 | + } |
| 148 | + if (f[i] != 0) { |
| 149 | + return f[i]; |
| 150 | + } |
| 151 | + int s = rides[i][0], e = rides[i][1], t = rides[i][2]; |
| 152 | + int j = search(rides, e, i + 1); |
| 153 | + long ans = Math.max(dfs(i + 1), dfs(j) + e - s + t); |
| 154 | + f[i] = ans; |
| 155 | + return ans; |
| 156 | + } |
| 157 | + |
| 158 | + private int search(int[][] rides, int x, int i) { |
| 159 | + int left = i, right = m; |
| 160 | + while (left < right) { |
| 161 | + int mid = (left + right) >> 1; |
| 162 | + if (rides[mid][0] >= x) { |
| 163 | + right = mid; |
| 164 | + } else { |
| 165 | + left = mid + 1; |
| 166 | + } |
| 167 | + } |
| 168 | + return left; |
| 169 | + } |
| 170 | +} |
| 171 | +``` |
| 172 | + |
| 173 | +```java |
| 174 | +class Solution { |
| 175 | + public long maxTaxiEarnings(int n, int[][] rides) { |
| 176 | + Arrays.sort(rides, (a, b) -> a[1] - b[1]); |
| 177 | + int m = rides.length; |
| 178 | + long[] dp = new long[m + 1]; |
| 179 | + for (int i = 0; i < m; ++i) { |
| 180 | + int s = rides[i][0], e = rides[i][1], t = rides[i][2]; |
| 181 | + int j = search(rides, s, i); |
| 182 | + dp[i + 1] = Math.max(dp[i], dp[j] + e - s + t); |
| 183 | + } |
| 184 | + return dp[m]; |
| 185 | + } |
| 186 | + |
| 187 | + private int search(int[][] rides, int x, int n) { |
| 188 | + int left = 0, right = n; |
| 189 | + while (left < right) { |
| 190 | + int mid = (left + right) >> 1; |
| 191 | + if (rides[mid][1] > x) { |
| 192 | + right = mid; |
| 193 | + } else { |
| 194 | + left = mid + 1; |
| 195 | + } |
| 196 | + } |
| 197 | + return left; |
| 198 | + } |
| 199 | +} |
| 200 | +``` |
| 201 | + |
| 202 | +### **C++** |
| 203 | + |
| 204 | +```cpp |
| 205 | +using ll = long long; |
| 206 | + |
| 207 | +class Solution { |
| 208 | +public: |
| 209 | + long long maxTaxiEarnings(int n, vector<vector<int>>& rides) { |
| 210 | + sort(rides.begin(), rides.end()); |
| 211 | + int m = rides.size(); |
| 212 | + vector<ll> f(m); |
| 213 | + vector<int> x(3); |
| 214 | + function<ll(int)> dfs = [&](int i) -> ll { |
| 215 | + if (i >= m) return 0; |
| 216 | + if (f[i]) return f[i]; |
| 217 | + int s = rides[i][0], e = rides[i][1], t = rides[i][2]; |
| 218 | + x[0] = e; |
| 219 | + int j = lower_bound(rides.begin() + i + 1, rides.end(), x, [&](auto& l, auto& r) -> bool { return l[0] < r[0];}) - rides.begin(); |
| 220 | + ll ans = max(dfs(i + 1), dfs(j) + e - s + t); |
| 221 | + f[i] = ans; |
| 222 | + return ans; |
| 223 | + }; |
| 224 | + return dfs(0); |
| 225 | + } |
| 226 | +}; |
| 227 | +``` |
| 228 | +
|
| 229 | +```cpp |
| 230 | +using ll = long long; |
| 231 | +
|
| 232 | +class Solution { |
| 233 | +public: |
| 234 | + long long maxTaxiEarnings(int n, vector<vector<int>>& rides) { |
| 235 | + sort(rides.begin(), rides.end(), [&](auto& l, auto& r) -> bool { return l[1] < r[1]; }); |
| 236 | + int m = rides.size(); |
| 237 | + vector<ll> dp(m + 1); |
| 238 | + vector<int> x(3); |
| 239 | + for (int i = 0; i < m; ++i) { |
| 240 | + int s = rides[i][0], e = rides[i][1], t = rides[i][2]; |
| 241 | + x[1] = s; |
| 242 | + int j = upper_bound(rides.begin(), rides.begin() + i, x, [&](auto& l, auto& r) -> bool { return l[1] < r[1]; }) - rides.begin(); |
| 243 | + dp[i + 1] = max(dp[i], dp[j] + e - s + t); |
| 244 | + } |
| 245 | + return dp[m]; |
| 246 | + } |
| 247 | +}; |
| 248 | +``` |
| 249 | + |
| 250 | +### **Go** |
| 251 | + |
| 252 | +```go |
| 253 | +func maxTaxiEarnings(n int, rides [][]int) int64 { |
| 254 | + sort.Slice(rides, func(i, j int) bool { return rides[i][0] < rides[j][0] }) |
| 255 | + m := len(rides) |
| 256 | + f := make([]int64, m) |
| 257 | + var dfs func(int) int64 |
| 258 | + dfs = func(i int) int64 { |
| 259 | + if i >= m { |
| 260 | + return 0 |
| 261 | + } |
| 262 | + if f[i] != 0 { |
| 263 | + return f[i] |
| 264 | + } |
| 265 | + s, e, t := rides[i][0], rides[i][1], rides[i][2] |
| 266 | + j := sort.Search(m, func(k int) bool { return rides[k][0] >= e }) |
| 267 | + ans := max(dfs(i+1), dfs(j)+int64(e-s+t)) |
| 268 | + f[i] = ans |
| 269 | + return ans |
| 270 | + } |
| 271 | + return dfs(0) |
| 272 | +} |
| 273 | + |
| 274 | +func max(a, b int64) int64 { |
| 275 | + if a > b { |
| 276 | + return a |
| 277 | + } |
| 278 | + return b |
| 279 | +} |
| 280 | +``` |
| 281 | + |
| 282 | +```go |
| 283 | +func maxTaxiEarnings(n int, rides [][]int) int64 { |
| 284 | + sort.Slice(rides, func(i, j int) bool { return rides[i][1] < rides[j][1] }) |
| 285 | + m := len(rides) |
| 286 | + dp := make([]int64, m+1) |
| 287 | + for i, ride := range rides { |
| 288 | + s, e, t := ride[0], ride[1], ride[2] |
| 289 | + j := sort.Search(m, func(k int) bool { return rides[k][1] > s }) |
| 290 | + dp[i+1] = max(dp[i], dp[j]+int64(e-s+t)) |
| 291 | + } |
| 292 | + return dp[m] |
| 293 | +} |
69 | 294 |
|
| 295 | +func max(a, b int64) int64 { |
| 296 | + if a > b { |
| 297 | + return a |
| 298 | + } |
| 299 | + return b |
| 300 | +} |
70 | 301 | ```
|
71 | 302 |
|
72 | 303 | ### **...**
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