http://www.51nod.com/Challenge/Problem.html#!#problemId=1791

先用棧找出每個右括號向左能匹配多遠 這樣是找出了所有獨立的合法序列 然後再算上兩兩拼接而成的新合法序列 dp陣列維護一下就好

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn=2e6+10;

stack <int> stk;
ll dp[maxn];
int pos[maxn];
int n;
char ch[maxn];

void init()
{
    int i,p;
    while(!stk.empty()) stk.pop();
    for(i=1;i<=n;i++) pos[i]=-1;
    for(i=1;i<=n;i++){
        if(ch[i]=='(') stk.push(i);
        else{
            if(!stk.empty()){
                p=stk.top();
                stk.pop();
                pos[i]=p-1;
            }
        }
    }
}

ll solve()
{
    ll res;
    int i;
    for(i=1;i<=n;i++) dp[i]=0;
    res=0;
    for(i=1;i<=n;i++){
        if(pos[i]!=-1) dp[i]=dp[pos[i]]+1;
        res+=dp[i];
    }
    return res;
}

int main()
{
    int t;
    scanf("%d",&t);
    while(t--){
        scanf("%s",ch+1);
        n=strlen(ch+1);
        init();
        printf("%lld\n",solve());
    }
    return 0;
}