hihocoder #1300 : 展胜地的鲤鱼旗 dp

#include<iostream>
#include<cstdio>
#include<stack>
using namespace std;

typedef long long LL;
const int maxn = 1e6 + 10;

char str[maxn];
LL dp[maxn];
int pos[maxn];

void init() {
    memset(pos, 0, sizeof(pos));
    memset(dp, 0, sizeof(dp));
}

int main() {
    while (scanf("%s", str + 1) == 1) {
        int len = strlen(str + 1);
        init();
        stack<int> ms;
        for (int i = 1; i <= len; i++) {
            if (str[i] == ‘(‘) {
                ms.push(i);
            }
            else {
                if (!ms.empty()) {
                    int j = ms.top(); ms.pop();
                    pos[i] = j;
                }
            }
        }
        LL ans = 0;
        for (int i = 1; i <= len; i++) {
            if(pos[i]>=1) dp[i] = dp[pos[i] - 1] + 1;
            ans += dp[i];
        }
        printf("%lld\n", ans);
    }
    return 0;
}