【FZU2190】非提的救赎【单调栈】

#include <iostream>
#include <cstdio>
#include <string>
#include <string.h>
#include <algorithm>
using namespace std;

const int MaxN=2010;
long long dp[MaxN];
int up[MaxN];
int stack[MaxN];
int top;
char s[MaxN];
long long ans;
int push(int x)
{
while(top&&up[stack[top-1]]>=up[x])
--top;
stack[top++]=x;
if(top>1)
return stack[top-2];
else
return 0;
}

int main()
{
int N,M;
int cou;
while(~scanf("%d %d",&N,&M))
{
ans=0;
memset(up,0,sizeof up);
while(N--)
{
scanf("%s",s+1);
dp[0]=0;
top=0;
for(int i=1;i<=M;++i)
{
if(s[i]=='w')
++up[i];
else
up[i]=0;
cou=push(i);
dp[i]=dp[cou]+(i-cou)*up[i];
ans+=dp[i];
}
}
printf("%lld\n",ans);
}
return 0;
}