poj 1458 最长公共子序列

来源：互联网发布：网络博客代理编辑：程序博客网时间：2024/06/02 02:40

迭代版：

#include<iostream>#include<cstdio>#include<algorithm>#include<cstring>using namespace std;const int M=310;typedef char ELEM;ELEM X[M];ELEM Y[M];int c[M][M];int LCS_LENGTH(int XLen,int YLen){//cout<<XLen<<" "<<YLen<<endl;    for(int i=1;i<=XLen;i++) c[i][0]=0;    for(int j=0;j<=YLen;j++) c[0][j]=0;    for(int i=1;i<=XLen;i++)        for(int j=1;j<=YLen;j++){//cout<<i<<" "<<X[i]<<" "<<j<<" "<<Y[j]<<endl;            if(X[i]==Y[j]){ c[i][j]=c[i-1][j-1]+1;}            else if(c[i-1][j]>=c[i][j-1]){ c[i][j]=c[i-1][j]; }            else{ c[i][j]=c[i][j-1]; }}    return c[XLen][YLen];}int main(){    //freopen("memoized lcs.txt","r",stdin);    while(cin>>X+1>>Y+1){        cout<<LCS_LENGTH(strlen(X+1),strlen(Y+1))<<endl;//        for(int i=0;i<=strlen(X+1);i++){//            for(int j=0;j<=strlen(Y+1);j++) cout<<c[i][j]<<" ";//            cout<<endl;}    }    return 0;}

带备忘递归版：

//要用负数（此处是-1）来表示未被计算的LCS长度，不能用0。因为LCS长度有可能为0。故遇到c[i][j]=0时，以为未被计算（会再次递归），其实很多时候已算，故TLE了#include<iostream>#include<cstring>#include<cstdio>using namespace std;const int M=310;typedef char ELEM;ELEM X[M];ELEM Y[M];int c[M][M];int MEMOIZED_LCS_LENGTH(int i,int j){    if(i==0||j==0) return c[i][j]=0;    if(c[i][j]>=0) return c[i][j];    if(X[i]==Y[j]) return c[i][j]=MEMOIZED_LCS_LENGTH(i-1,j-1)+1;    else return c[i][j]=max(MEMOIZED_LCS_LENGTH(i-1,j),MEMOIZED_LCS_LENGTH(i,j-1));}int main(){    //freopen("lcs.txt","r",stdin);    while(scanf("%s%s",X+1,Y+1)==2){        int XLen=strlen(X+1),YLen=strlen(Y+1);        memset(c,-1,sizeof(c));//        c=new int*[XLen+5];//        for(int i=0;i<=XLen;i++) c[i]=new int[YLen+5]();        printf("%d\n",MEMOIZED_LCS_LENGTH(XLen,YLen));//        for(int i=0;i<=strlen(X+1);i++){//            for(int j=0;j<=strlen(Y+1);j++) cout<<c[i][j]<<" ";//            cout<<endl;}//        for(int i=0;i<=XLen;i++) delete[] c[i];//        delete[] c;    }    return 0;}

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