dp：最长公共子序列问题

#include<iostream>
#include <cstring>
#include <vector>
#include <algorithm>

using namespace std;

const int N = 1010;
int m, n;
char a[N], b[N];
int f[N][N];  // 生命全局全为0保证r1 c1 都是 0 

int main()
{
    
    
    cin >> m >> n;
    scanf("%s%s", a + 1, b + 1); 
    for (int i = 1; i <= m; i++){
    
    
        for (int j = 1; j <= n; j++){
    
    
            if (a[i] == b[j])
                f[i][j] =f[i - 1][j - 1] + 1;
            else
                f[i][j] = max(f[i - 1][j], f[i][j - 1]);
        }
    }
    cout << f[m][n];
    return 0;
    
}

STL

#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
using namespace std;
int main(void) {
    
    
    int leng1, leng2;
    cin >> leng1 >> leng2;

    string str1, str2;
    cin >> str1 >> str2;

    vector<vector<int>>dp(leng1 + 1, vector<int>(leng2 + 1));

    for (int i = 0; i < leng1; ++i) {
    
    
        for (int j = 0; j < leng2; ++j) {
    
    
            if (str1[i] == str2[j])
                dp[i + 1][j + 1] = dp[i][j] + 1;
            else
                dp[i + 1][j + 1] = max(dp[i + 1][j], dp[i][j + 1]);
        }
    }
    cout << dp.back().back() << endl;
    return 0;
}

腾讯的笔试题

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 1001;
int f[N][N];


int LCS(string& s1, string& s2) {
    
    
	int m = s1.size(), n = s2.size();
	for (int i = 0; i < m; i++)
		f[i][0] = 0;
	for (int i = 0; i < n; i++)
		f[0][i] = 0;

	for (int i = 1; i <= m; i++) {
    
    
		for (int j = 1; j <=n; j++) {
    
    
			if (s1[i-1] == s2[j-1])
				f[i][j] = f[i - 1][j - 1] + 1;
			else
				f[i][j] = max(f[i - 1][j], f[i][j - 1]);
		}
	}
	return f[m][n];
}
int main() {
    
    
	string s;
	while (cin >> s) {
    
    
		int len = s.size();
		if (len == 1) {
    
    
			cout << 1 << endl;
			continue;
		}		
		string copy = s;
		reverse(copy.begin(), copy.end());
		int maxlen = LCS(s, copy);
		int res = len - maxlen;
		cout << res << endl;
	}
	return 0;
}