最长公共子序列_最长公共子串

最长公共子串

int m = s.length(),n=s2.length();
int[][] dp = new int[m+1][n+1];
int max_=0;
for(int i=1; i<=m; i++) {
    for(int j=1; j<=n; j++) {
        //第i个字符，下标是i-1
        if(s.charAt(i-1)==s2.charAt(j-1))
            dp[i][j]=dp[i-1][j-1]+1;
        else
            dp[i][j]=0;
        max_ = dp[i][j]>max_?dp[i][j]:max_;
    }
}

return max_;

最长公共子序列

获取最长公共子序列

String s = "abcdded";
String s2 = "adde";
//获取最长公共子序列
int m = s.length(),n=s2.length();
int[][] dp = new int[m+1][n+1];

int max_=0;
for(int i=1; i<=m; i++) {
    for(int j=1; j<=n; j++) {
        //第i个字符，下标是i-1
        if(s.charAt(i-1)==s2.charAt(j-1))
            dp[i][j]=dp[i-1][j-1]+1;
        else
            dp[i][j]=Math.max(dp[i][j-1], dp[i-1][j]);
        max_ = dp[i][j]>max_?dp[i][j]:max_;
    }
}
return max_;

获取最长公共子序列和子序列是谁

//获取最长公共子序列和子序列是谁
//sb是子序列，lcs返回最长长度
public static int lcs(String word1, String word2, StringBuilder sb) {
    int m=word1.length(),n=word2.length();
    int[][] res = new int[m+1][n+1];
    String[][] flag = new String[m+1][n+1];
    int max=0;

    for(int i=1; i<=m; i++){
        for(int j=1; j<=n; j++) {
            if(word1.charAt(i-1)==word2.charAt(j-1)){
                res[i][j]=res[i-1][j-1]+1;
                flag[i][j]="ok";
            }else{
                if(res[i-1][j]>res[i][j-1]) {
                    flag[i][j]="up";
                }else flag[i][j]="left";
                res[i][j]=Math.max(res[i-1][j], res[i][j-1]);
            }
            if(res[i][j]>max) {
                max=res[i][j];
            }
        }
    }
    printLcs(flag, word1, m, n, sb);
    return max;

}
public static void printLcs(String[][] flag, String s1, int i, int j, StringBuilder sb) {
    //为0时，表明该字符串没有字符参与，是从1开始的
    if(i==0 || j==0) return ;
    if(flag[i][j]=="ok") {

        printLcs(flag, s1, i-1, j-1, sb);
        sb.append(s1.charAt(i-1));
    }else if(flag[i][j]=="left") printLcs(flag, s1, i, j-1, sb);
    else if(flag[i][j]=="up") printLcs(flag, s1, i-1, j, sb);
}