contest-888-A 单调栈 前缀

#include <bits/stdc++.h>

#define  _debug(x) cerr<<#x<<" = "<<x<<endl
using namespace std;
typedef long long ll;
const int MAXN = 3e3 + 59;
typedef long long ll;

int n, m;
struct {
    int up, ls;
} stk[MAXN];

int up[MAXN][MAXN]; //consecutive 1 above (i,j) (included)
int pr[MAXN][MAXN]; //pre sum 1 in the left of (i,j) (included)
char str[MAXN];
int top;
ll ans;

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    ans = 0;
    cin >> n >> m;

    for (int i = 1; i <= n; ++i) {
        cin >> (str + 1);
        for (int j = 1; j <= m; ++j) {
            up[i][j] = (str[j] == '1') ? (up[i - 1][j] + 1) : 0;
            pr[i][j] = pr[i][j - 1] + (str[j] - '0');
        }
    }

    for (int i = 1; i <= n; ++i) {
        top = 0;
        for (int j = 1, k; j <= m + 1; ++j) {
            k = j;
            while (top && stk[top].up >= up[i][j]) {
                k = stk[top].ls;
                if (stk[top].up > up[i][j]) {
                    int l = stk[top].ls;
                    int r = j - 1;
                    if (pr[i + 1][r] - pr[i + 1][l - 1] != r - l + 1) {
                        ans++;
                    }
                }
                top--;
            }
            if (up[i][j])stk[++top] = {up[i][j], k};
        }
//        while (top) {
//            int l = stk[top].ls;
//            int r = m;
//            if (pr[i + 1][r] - pr[i + 1][l - 1] != r - l + 1) {
//                ans++;
//            }
//            top--;
//        }
    }
    cout << ans << endl;
    return 0;
}