73. Set Matrix Zeroes

public static void setZeroes(int[][] matrix) {
         if(matrix == null || matrix.length == 0 ) {
             return ;
         }
         int[] path = new int[matrix.length*matrix[0].length];
         int count = 0;
         for(int i = 0; i < matrix.length; i++) {
             for(int j = 0; j < matrix[0].length; j++) {
                 if(matrix[i][j] == 0) {
                     path[count++] = i * matrix[0].length+j;
                 }
             }
         }
         for(int i = 0; i < count; i++) {
             int rol = path[i] / matrix[0].length;
             int col = path[i] % matrix[0].length;
             int j = 0;
             while(j < matrix[0].length) {
                 matrix[rol][j++] = 0;
             }
             j = 0;
             while(j < matrix.length) {
                 matrix[j++][col] = 0;
             }
         }
    }
import numpy as np import pandas as pd import matplotlib.pyplot as plt plt.rcParams['font.sans-serif'] = ["SimHei"] # 单使用会使负号显示错误 plt.rcParams['axes.unicode_minus'] = False # 把负号正常显示 # 读取北京房价数据 path = 'data.txt' data = pd.read_csv(path, header=None, names=['房子面积', '房子价格']) print(data.head(10)) print(data.describe()) # 绘制散点图 data.plot(kind='scatter', x='房子面积', y='房子价格') plt.show() def computeCost(X, y, theta): inner = np.power(((X * theta.T) - y), 2) return np.sum(inner) / (2 * len(X)) data.insert(0, 'Ones', 1) cols = data.shape[1] X = data.iloc[:,0:cols-1]#X是所有行,去掉最后一列 y = data.iloc[:,cols-1:cols]#X是所有行,最后一列 print(X.head()) print(y.head()) X = np.matrix(X.values) y = np.matrix(y.values) theta = np.matrix(np.array([0,0])) print(theta) print(X.shape, theta.shape, y.shape) def gradientDescent(X, y, theta, alpha, iters): temp = np.matrix(np.zeros(theta.shape)) parameters = int(theta.ravel().shape[1]) cost = np.zeros(iters) for i in range(iters): error = (X * theta.T) - y for j in range(parameters): term = np.multiply(error, X[:, j]) temp[0, j] = theta[0, j] - ((alpha / len(X)) * np.sum(term)) theta = temp cost[i] = computeCost(X, y, theta) return theta, cost alpha = 0.01 iters = 1000 g, cost = gradientDescent(X, y, theta, alpha, iters) print(g) print(computeCost(X, y, g)) x = np.linspace(data.Population.min(), data.Population.max(), 100) f = g[0, 0] + (g[0, 1] * x) fig, ax = plt.subplots(figsize=(12,8)) ax.plot(x, f, 'r', label='Prediction') ax.scatter(data.Population, data.Profit, label='Traning Data') ax.legend(loc=2) ax.set_xlabel('房子面积') ax.set_ylabel('房子价格') ax.set_title('北京房价拟合曲线图') plt.show()
06-04
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