最大回文长度

回文

回文串就是一个正读和反读都一样的字符串，比如“level”或者“noon”等等就是回文串。

code(Java)

public class Huiwen {

    public static void main(String[] args) {
        ArrayList<String> list = new ArrayList<String>();
        Scanner in = new Scanner(System.in);
        int a = in.nextInt();
        while(in.hasNext()) {

            list.add(in.next());
            a--;
            if(a==0)
                break;

        }
        for(int i=0;i<list.size();i++)
        {
            String s = list.get(i);
            int maxlen = maxHuiwen(s);
            System.out.println(maxlen);
        }

    }
    public static int maxHuiwen(String string)
    {
        int max=0;
        if(string == null || string == "")
            return 0;
        char[] a=string.toCharArray();
        for (int i = 0; i < string.length(); i++) {
            for (int j = 0; i+j<string.length()&&i-j>=0; j++) {
                if (a[i-j]!=a[i+j]) {
                    break;
                }
                if (2*j+1>max) {
                    max=2*j+1;
                }
            }
            //偶数

for (int j = 0; i+j+1 < a.length&&i-j>=0; j++) {
                if (a[i-j]!=a[i+j+1]) {
                    break;
                }
                if (j*2+2>max) {
                    max=j*2+2;
                }
            }
        }
        return max;
        //System.out.println(max);
    }

}

code(C++)

#include <cstdio>
#include <cstring>
#include <string.h>
char str[1000002 + 1200];

int fast(char *p)
{
    int ans = 1;
    for (int i = 1; p[i]; ++i)
    {
        int s = i, e = i, t;
        //略过相同的
        while (p[e + 1] == p[i]) ++e;
        i = e;
        //略过相同的之后判断
        while (p[s - 1] == p[e + 1]) --s, ++e;
        if ((t = e - s + 1) > ans) ans = t;
    }
    return ans;
}

int main()
{
    str[0]='$';
    int n;
    scanf("%d", &n);
    while (n --) {
        scanf("%s", str + 1);
        printf("%d\n", fast(str));
    }
    return 0;
}