UVa 10405: Longest Common Subsequence

经典的求最长公共子序列（Longest Common Subsequence， LCS） 的一道题，动态规划妥妥的。
要注意的地方是输入的串可能是空串，所以不要用cin。

我的解题代码如下：

#include <iostream>#include <cstdio>#include <cstring>using namespace std;#define MAXN 1005#define max(a,b) ((a)>(b)?(a):(b))//#define min(a,b) ((a)<(b)? (a):(b))char s1[MAXN], s2[MAXN];int lcsl[2][MAXN];int main(){while(gets(s1)!=NULL){gets(s2);int len1 = strlen(s1);int len2 = strlen(s2);if(!len1 || !len2) { cout << 0 << endl; continue; }int longestlen = 0;for(int j=0; j<=len2; j++) lcsl[0][j] = 0;for(int i=1; i<=len1; i++){lcsl[i%2][0] = 0;for(int j=1; j<=len2; j++){if(s1[i-1]==s2[j-1]) lcsl[i%2][j] = lcsl[(i-1)%2][j-1] + 1;else lcsl[i%2][j] = max( lcsl[(i-1)%2][j] , lcsl[i%2][j-1] );longestlen = max( longestlen , lcsl[i%2][j] );}}cout << longestlen << endl;}return 0;}

其中lcsl数组存放以s1的第i个字符结尾以s2的第j个字符结尾的LCS的长度，我只开了两个一维数组以节省空间。

附上题目如下：

Sequence 1:                

Sequence 2:                


Given two sequences of characters, print the length of the longest common subsequence of both sequences. For example, the longest common subsequence of the following two sequences:

abcdghaedfhr

is adh of length 3.

Input consists of pairs of lines. The first line of a pair contains the first string and the second line contains the second string. Each string is on a separate line and consists of at most 1,000 characters

For each subsequent pair of input lines, output a line containing one integer number which satisfies the criteria stated above.

Sample input

a1b2c3d4ezz1yy2xx3ww4vvabcdghaedfhrabcdefghijklmnopqrstuvwxyza0b0c0d0e0f0g0h0i0j0k0l0m0n0o0p0q0r0s0t0u0v0w0x0y0z0abcdefghijklmnzyxwvutsrqpoopqrstuvwxyzabcdefghijklmn

Output for the sample input

432614