Leetcode——二维数组及滚动数组练习

118. 杨辉三角

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
    // 定义二维数组
        vector<vector<int>> num(numRows);
        for(int i=0;i<numRows;i++){
        	//这里是给内层vector定义大小。默认是0,这里n是个数，不是值
            num[i].resize(i + 1);
            num[i][0] = num[i][i] = 1;
            for (int j = 1; j < i; ++j) {
                num[i][j] = num[i - 1][j] + num[i - 1][j - 1];
        }
    }
    return num;
    }
};

119. 杨辉三角 II

class Solution {
public:
    vector<int> getRow(int rowIndex) {
        vector<vector<int>> num(rowIndex + 1);
        vector<int> num1;
        for (int i = 0; i <= rowIndex; ++i) {
            num[i].resize(i + 1);
            num[i][0] = num[i][i] = 1;
            for (int j = 1; j < i; ++j) {
                num[i][j] = num[i - 1][j] + num[i - 1][j - 1];
                if (i == rowIndex) {
                    num1.push_back(num[i][j]);
                }
            }
        }
        if (rowIndex > 0) {
            num1.insert(num1.begin(), num[rowIndex][0]);
        }
        num1.push_back(num[rowIndex][rowIndex]);
        return num1;
    }
};

661. 图片平滑器

有思路但没写出来（复习）

class Solution {
public:
    vector<vector<int>> imageSmoother(vector<vector<int>>& img) {
        int m = img.size(), n = img[0].size();
        vector<vector<int>> ret(m, vector<int>(n));
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                int num = 0, sum = 0;
                for (int x = i - 1; x <= i + 1; x++) {
                    for (int y = j - 1; y <= j + 1; y++) {
                        if (x >= 0 && x < m && y >= 0 && y < n) {
                            num++;
                            sum += img[x][y];
                        }
                    }
                }
                ret[i][j] = sum / num;
            }
        }
        return ret;
    }
};

598. 范围求和 II

class Solution {
public:
    int maxCount(int m, int n, vector<vector<int>>& ops) {
        int mina = m, minb = n;
        for (const auto& op: ops) {
            mina = min(mina, op[0]);
            minb = min(minb, op[1]);
        }
        return mina * minb;
    }
};