for (int k = i; k < j; k++) {
    if (op[k] == 't') {
        dp[i][j][0] = max(dp[i][j][0], dp[i][k][0] + dp[k + 1][j][0]);
        dp[i][j][1] = min(dp[i][j][1], dp[i][k][1] + dp[k + 1][j][1]);
    } else {
        dp[i][j][0] = max(dp[i][j][0], max(dp[i][k][1] * dp[k + 1][j][1], dp[i][k][0] * dp[k + 1][j][0]));
        dp[i][j][1] = min(dp[i][j][1], min(dp[i][k][1] * dp[k + 1][j][1], min(dp[i][k][0] * dp[k + 1][j][0], min(dp[i][k][1] * dp[k + 1][j][0], dp[i][k][0] * dp[k + 1][j][1]))));
    }
}

for (int k = i + 1; k <= j; k++) {
    if (op[k] == 't') {
        dp[i][j][0] = max(dp[i][j][0], dp[i][k - 1][0] + dp[k][j][0]);
        dp[i][j][1] = min(dp[i][j][1], dp[i][k - 1][1] + dp[k][j][1]);
    } else {
        dp[i][j][0] = max(dp[i][j][0], max(dp[i][k - 1][1] * dp[k][j][1], dp[i][k - 1][0] * dp[k][j][0]));
        dp[i][j][1] = min(dp[i][j][1], min(dp[i][k - 1][1] * dp[k][j][1], min(dp[i][k - 1][0] * dp[k][j][0], min(dp[i][k - 1][1] * dp[k][j][0], dp[i][k - 1][0] * dp[k][j][1]))));
    }
}

第一个里两个子区间是 $[i,k]$ 和 $[k+1,j]$，$k \in [i,j)$。第二个里两个子区间是 $[i,k-1]$ 和 $[k,j]$，$k \in (i,j]$。为什么第一个会 $\sf WA$ 第二个能 $\sf AC$。/yiw