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总时间限制:
- 1000ms 内存限制:
- 65536kB
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描述
- Given three strings, you are to determine whether the third string can be formed by combining the characters in the first two strings. The first two strings can be mixed arbitrarily, but each must stay in its original order.
For example, consider forming "tcraete" from "cat" and "tree":
String A: cat
String B: tree
String C: tcraete
As you can see, we can form the third string by alternating characters from the two strings. As a second example, consider forming "catrtee" from "cat" and "tree":
String A: cat
String B: tree
String C: catrtee
Finally, notice that it is impossible to form "cttaree" from "cat" and "tree".
输入 - The first line of input contains a single positive integer from 1 through 1000. It represents the number of data sets to follow. The processing for each data set is identical. The data sets appear on the following lines,
one data set per line.
For each data set, the line of input consists of three strings, separated by a single space. All strings are composed of upper and lower case letters only. The length of the third string is always the sum of the lengths of the first two strings. The first two strings will have lengths between 1 and 200 characters, inclusive.
输出 - For each data set, print:
Data set n: yes
if the third string can be formed from the first two, or
Data set n: no
if it cannot. Of course n should be replaced by the data set number. See the sample output below for an example.
样例输入 -
3 cat tree tcraete cat tree catrtee cat tree cttaree
样例输出 -
Data set 1: yes Data set 2: yes
Data set 3: no
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/* * 1. dp[i][j]表示 s1的前i位和s2的前j位 组成满足题意的 s3[0..i+j] 2. 边界条件 dp[0][0] = 1 3. 状态转移方程: 1. if(dp[j - 1][k]==1 && s1[j-1] == s3[j + k -1]) dp[j][k] = 1; 2. if(dp[j][k - 1]==1 && s2[k-1] == s3[j + k-1]) dp[j][k] = 1; */ #include "iostream" #include "cstring" using namespace std; int main() { char s1[201]; char s2[201]; char s3[401]; int dp[201][201]; int n; cin >> n; for (int i = 1; i <= n; i++) { cin >> s1 >> s2 >> s3; memset(dp, 0, sizeof(dp)); dp[0][0] = 1; int len1 = strlen(s1); int len2 = strlen(s2); for (int j = 0; j <= len1; j++) for (int k = 0; k <= len2; k++) { if (j>0 && dp[j - 1][k]==1 && s1[j-1] == s3[j + k -1]) dp[j][k] = 1; if (k>0 && dp[j][k - 1]==1 && s2[k-1] == s3[j + k-1]) dp[j][k] = 1; } printf("Data set %d: ", i); if (dp[len1][len2]) cout << "yes" << endl; else cout << "no" << endl; } return 0; }

本文介绍了一个算法问题,即判断第三字符串是否能通过前两个字符串的字符按原顺序组合而成。文章给出了具体的输入输出示例,并提供了使用动态规划解决该问题的C++实现代码。
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