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29 | 29 | <strong>输入:</strong>s = "babgbag", t = "bag"
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30 | 30 | <code><strong>输出</strong></code><strong>:</strong><code>5
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31 | 31 | </code><strong>解释:</strong>
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32 |
| -如下图所示, 有 5 种可以从 s 中得到 <code>"bag" 的方案</code>。 |
| 32 | +如下图所示, 有 5 种可以从 s 中得到 <code>"bag" 的方案</code>。 |
33 | 33 | <code><strong><u>ba</u></strong>b<u><strong>g</strong></u>bag</code>
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34 | 34 | <code><strong><u>ba</u></strong>bgba<strong><u>g</u></strong></code>
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35 | 35 | <code><u><strong>b</strong></u>abgb<strong><u>ag</u></strong></code>
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54 | 54 |
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55 | 55 | <!-- 这里可写通用的实现逻辑 -->
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56 | 56 |
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| 57 | +动态规划,`dp[i][j]` 表示 `s[:i]` 的子序列中 `t[:j]` 的出现次数 |
| 58 | + |
57 | 59 | <!-- tabs:start -->
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58 | 60 |
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59 | 61 | ### **Python3**
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60 | 62 |
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61 | 63 | <!-- 这里可写当前语言的特殊实现逻辑 -->
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62 | 64 |
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63 | 65 | ```python
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64 |
| - |
| 66 | +class Solution: |
| 67 | + def numDistinct(self, s: str, t: str) -> int: |
| 68 | + m, n = len(s), len(t) |
| 69 | + dp = [[0] * (n + 1) for _ in range(m + 1)] |
| 70 | + for i in range(m + 1): |
| 71 | + dp[i][0] = 1 |
| 72 | + for i in range(1, m + 1): |
| 73 | + for j in range(1, n + 1): |
| 74 | + dp[i][j] = dp[i - 1][j] |
| 75 | + if s[i - 1] == t[j - 1]: |
| 76 | + dp[i][j] += dp[i - 1][j - 1] |
| 77 | + return dp[m][n] |
65 | 78 | ```
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66 | 79 |
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67 | 80 | ### **Java**
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68 | 81 |
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69 | 82 | <!-- 这里可写当前语言的特殊实现逻辑 -->
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70 | 83 |
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71 | 84 | ```java
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| 85 | +class Solution { |
| 86 | + public int numDistinct(String s, String t) { |
| 87 | + int m = s.length(); |
| 88 | + int n = t.length(); |
| 89 | + int[][] dp = new int[m + 1][n + 1]; |
| 90 | + for (int i = 0; i <= m; i++) { |
| 91 | + dp[i][0] = 1; |
| 92 | + } |
| 93 | + for (int i = 1; i <= m; i++) { |
| 94 | + for (int j = 1; j <= n; j++) { |
| 95 | + dp[i][j] = dp[i - 1][j]; |
| 96 | + if (s.charAt(i - 1) == t.charAt(j - 1)) { |
| 97 | + dp[i][j] += dp[i - 1][j - 1]; |
| 98 | + } |
| 99 | + } |
| 100 | + } |
| 101 | + return dp[m][n]; |
| 102 | + } |
| 103 | +} |
| 104 | +``` |
| 105 | + |
| 106 | +### **Go** |
| 107 | + |
| 108 | +```go |
| 109 | +func numDistinct(s string, t string) int { |
| 110 | + m, n := len(s), len(t) |
| 111 | + dp := make([][]int, m+1) |
| 112 | + for i := 0; i <= m; i++ { |
| 113 | + dp[i] = make([]int, n+1) |
| 114 | + dp[i][0] = 1 |
| 115 | + } |
| 116 | + for i := 1; i <= m; i++ { |
| 117 | + for j := 1; j <= n; j++ { |
| 118 | + dp[i][j] = dp[i-1][j] |
| 119 | + if s[i-1] == t[j-1] { |
| 120 | + dp[i][j] += dp[i-1][j-1] |
| 121 | + } |
| 122 | + } |
| 123 | + } |
| 124 | + return dp[m][n] |
| 125 | +} |
| 126 | +``` |
72 | 127 |
|
| 128 | +### **C++** |
| 129 | + |
| 130 | +```cpp |
| 131 | +class Solution { |
| 132 | +public: |
| 133 | + int numDistinct(string s, string t) { |
| 134 | + int m = s.size(), n = t.size(); |
| 135 | + vector<vector<unsigned long long>> dp(m + 1, vector<unsigned long long>(n + 1)); |
| 136 | + for (int i = 0; i <= m; ++i) { |
| 137 | + dp[i][0] = 1; |
| 138 | + } |
| 139 | + for (int i = 1; i <= m; ++i) { |
| 140 | + for (int j = 1; j <= n; ++j) { |
| 141 | + dp[i][j] = dp[i - 1][j]; |
| 142 | + if (s[i - 1] == t[j - 1]) { |
| 143 | + dp[i][j] += dp[i - 1][j - 1]; |
| 144 | + } |
| 145 | + } |
| 146 | + } |
| 147 | + return dp[m][n]; |
| 148 | + } |
| 149 | +}; |
73 | 150 | ```
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74 | 151 |
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75 | 152 | ### **...**
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