poj2955括号匹配 区间DP

#include<stdio.h>
#include<string.h>
const int maxn = 120;
char s[maxn];
int dp[maxn][maxn];
int max(int x,int y)
{
    return x>y?x:y;
}
int main()
{
    int i,j,k;
    while(scanf("%s",s))
    {
        if(strcmp(s,"end")==0)
            break;
        int len=strlen(s);
        memset(dp,0,sizeof(dp));
        for(k=1;k<len;k++)
        {
            for(i=0;i<len-k;i++)
            {
                if((s[i]==‘(‘&&s[i+k]==‘)‘)||(s[i]==‘[‘&&s[i+k]==‘]‘))
                    dp[i][i+k]=max(dp[i][i+k],dp[i+1][i+k-1]+1);
                for(j=i;j<i+k;j++)
                {
                    dp[i][i+k]=max(dp[i][i+k],dp[i][j]+dp[j+1][i+k]);
                }
            }
        }
        printf("%d\n",dp[0][len-1]*2);
    }
}