115.不同的子序列
本题递推公式与初始化最为重要。
cpp
class Solution {
public:
int numDistinct(string s, string t) {
vector<vector<uint64_t>> dp(s.size() + 1, vector<uint64_t>(t.size() + 1, 0));
for (int i = 0; i <= s.size(); ++i)
dp[i][0] = 1;
for (int i = 1; i <= s.size(); ++i) {
for (int j = 1; j <= t.size(); ++j) {
if (s[i - 1] == t[j - 1])
dp[i][j] = dp[i - 1][j - 1] + dp[i - 1][j];
else
dp[i][j] = dp[i - 1][j];
}
}
return dp[s.size()][t.size()];
}
};
583. 两个字符串的删除操作
cpp
class Solution {
public:
int minDistance(string word1, string word2) {
vector<vector<int>> dp(word1.size() + 1,
vector<int>(word2.size() + 1, 0));
for (int i = 1; i <= word1.size(); ++i)
dp[i][0] = i;
for (int j = 1; j <= word2.size(); ++j)
dp[0][j] = j;
for (int i = 1; i <= word1.size(); ++i) {
for (int j = 1; j <= word2.size(); ++j) {
if (word1[i - 1] == word2[j - 1])
dp[i][j] = dp[i - 1][j - 1];
else
dp[i][j] = min(dp[i - 1][j], dp[i][j - 1]) + 1;
}
}
return dp[word1.size()][word2.size()];
}
};
72. 编辑距离
cpp
class Solution {
public:
int minDistance(string word1, string word2) {
vector<vector<int>> dp(word1.size() + 1, vector<int>(word2.size() + 1, 0));
for (int i = 1; i <= word1.size(); ++i)
dp[i][0] = i;
for (int j = 1; j <= word2.size(); ++j)
dp[0][j] = j;
for (int i = 1; i <= word1.size(); ++i) {
for (int j = 1; j <= word2.size(); ++j) {
if (word1[i - 1] == word2[j - 1])
dp[i][j] = dp[i-1][j-1];
else
dp[i][j] = min(min(dp[i-1][j-1]+1,dp[i][j-1]+1), dp[i-1][j]+1);
}
}
return dp[word1.size()][word2.size()];
}
};