CS106B Assignment1

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Foreword

记录2022 winter的CS106B Assignment1

StackOverflow

熟悉栈溢出，观察Cycle是137 164 685 203 327 549

Only Connect

用递归方式去掉元音

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string onlyConnectize(string phrase) {
    if (phrase.length() == 0) {
        return "";
    } else if (!isalpha(phrase[0])) {
        if (phrase.length() == 1) {
            return "";
        } else {
            return onlyConnectize(phrase.substr(1));
        }
    }
    phrase[0] = toUpperCase(phrase[0]);
    if (phrase[0] == 'A' || phrase[0] == 'E' || phrase[0] == 'I' || phrase[0] == 'O' || phrase[0] == 'U') {
        if (phrase.length() == 1) {
            return "";
        } else {
            return onlyConnectize(phrase.substr(1));
        }
    }
    if (phrase.length() == 1) {
        string res = "";
        res += phrase[0];
        return res;
    } else {
        string res = "";
        res += phrase[0];
        res += onlyConnectize(phrase.substr(1));
        return res;
    }
}

Playing Fair

还是递归小练习，对于负数要抛出异常

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string aSequenceOfOrder(int n) {
    if (n == 0) {
        return "A";
    } else if (n < 0) {
        error("n should be greater than or equal zero.");
        return "";
    } else {
        return aSequenceOfOrder(n - 1) + bSequenceOfOrder(n - 1);
    }
    return "";
}

string bSequenceOfOrder(int n) {
    if (n == 0) {
        return "B";
    } else if (n < 0) {
        error("n should be greater than or equal zero.");
        return "";
    } else {
        return bSequenceOfOrder(n - 1) + aSequenceOfOrder(n - 1);
    }
}

Sandpiles

递归练习，模拟丢沙子

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const int dx[] = {-1, 1, 0, 0};
const int dy[] = {0, 0, -1, 1};

void dropSandOn(Grid<int>& world, int row, int col) {
    if (!world.inBounds(row, col)) {
        return;
    } else if (world[row][col] <= 2) {
        world[row][col] += 1;
        return;
    } else {
        world[row][col] = 0;
        for (int i = 0; i < 4; ++i) {
            int nrow = row + dx[i], ncol = col + dy[i];
            if (!world.inBounds(nrow, ncol)) {
                continue;
            }
            dropSandOn(world, nrow, ncol);
        }
        return;
    }
}

Plotter

模拟绘图仪，熟悉Stanford的库

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void runPlotterScript(istream& input) {
    PenStyle style = {1, "black"};
    bool is_up = true;
    double curx = 0.0, cury = 0.0;
    for (string line; getline(input, line); ) {
        Vector<string> opt = stringSplit(line, " ");
        opt[0] = toUpperCase(opt[0]);
        if (startsWith(opt[0], "PEND")) {
            is_up = false;
        } else if (startsWith(opt[0], "PENU")) {
            is_up = true;
        } else if (startsWith(opt[0], "MOVEA")) {
            if (!is_up) {
                drawLine(curx, cury, stringToReal(opt[1]), stringToReal(opt[2]), style);
            }
            curx = stringToReal(opt[1]), cury = stringToReal(opt[2]);
        } else if (startsWith(opt[0], "MOVER")) {
            if (!is_up) {
                drawLine(curx, cury, curx + stringToReal(opt[1]), cury + stringToReal(opt[2]), style);
            }
            curx = curx + stringToReal(opt[1]), cury = cury + stringToReal(opt[2]);
        } else if (startsWith(opt[0], "PENC")) {
            style.color = opt[1];
        } else {
            style.width = stringToReal(opt[1]);
        }
    }
}

效果

丢沙子

绘图仪