最长回文子序列

来源：互联网发布：伺服控制系统编程编辑：程序博客网时间：2024/05/16 15:16
#include <iostream>#include <ctime>using namespace std;void longest_palindrome(char *s,int **p,int length){for(int i=0;i<length-1;++i){//初始化数组相关信息p[i][i]=1;int j=i+1;if(s[i]==s[j]){p[i][j]=2;}else{p[i][j]=1;}}p[length-1][length-1]=1;//for(int i=length-3;i>=0;--i){//从后往前//for(int l=i+2;l<length;l++){//if(s[i]==s[l]){//p[i][l]=p[i+1][l-1]+2;//}else if(p[i+1][l]>p[i][l-1]){//p[i][l]=p[i+1][l];//}else{//p[i][l]=p[i][l-1];//}//}//}for(int l=3;l<=length;l++){//长度1和2都已记录，此处长度由3开始，从前往后for(int i=0;i<length-l+1;i++){int j=i+l-1;if(s[i]==s[j]){p[i][j]=p[i+1][j-1]+2;}else if(p[i+1][j]>p[i][j-1]){p[i][j]=p[i+1][j];}else{p[i][j]=p[i][j-1];}}}}void print_longest_palindrome(int **p,char *c,int n)//打印最长回文字符串{int length=p[0][n-1];char *cc=new char[length+1];cc[length]='\0';int i=0,j=n-1;//保存位置int low=0,high=length-1;//回文字符串中的上下下标while (i<j){while (p[i][j]==p[i+1][j]){++i;}cc[low++]=c[i];while(p[i][j]==p[i][j-1]){--j;}cc[high--]=c[j];++i;--j;}if(low==high){cc[low]=c[i];}for(int k=0;k<length;++k){cout<<cc[k];}cout<<endl;delete []cc;}int main(){srand((unsigned)time(NULL));int n=23;n=rand()%20+20;char *s=new char[n];/*s[0]='n',s[1]='m',s[2]='g',s[3]='s',s[4]='v',s[5]='g',s[6]='r',s[7]='i',s[8]='s',s[9]='m',s[10]='y',s[11]='g',s[12]='x',s[13]='p',s[14]='p',s[15]='e',s[16]='j',s[17]='x',s[18]='p',s[19]='q',s[20]='j',s[21]='a',s[22]='i';*/for(int i=0;i<n;++i){//if(rand()%2){s[i]=rand()%26+'a';cout<<s[i];/*}else{s[i]=rand()%26+'A';cout<<s[i];}*/}cout<<endl;int **p=new int*[n];for(int i=0;i<n;++i){//存储最长回问字符长度信息，并用此构建最长回文字符串p[i]=new int [n];}for(int i=0;i<n;++i){for(int j=0;j<n;++j){p[i][j]=0;}}longest_palindrome(s,p,n);for(int i=0;i<n;++i){for(int j=0;j<n;++j){cout<<p[i][j]<<" ";}cout<<endl;}cout<<endl;print_longest_palindrome(p,s, n);delete[]s;for(int i=0;i<n;++i){delete []p[i];}delete[]p;}
0 0