Amber-Leedcode-Java - 代码随想录打卡第38

Amber-Leedcode-Java - 代码随想录打卡第38 - 39天-动态规划汇总

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509. 斐波那契数

较为简单

746. 使用最小花费爬楼梯

62. 不同路径

一开始写的时候被吓到了，但是发现听完一半之后再写还是比较容易的

对于我而言主要是找到逻辑，

class Solution {public int uniquePaths(int m, int n) {if (m <= 1 || n <=1){return 1;}int[][] result = new int[m][n];result[0][0] = 0;result[1][0] = 1;result[0][1] = 1;for (int i = 0;i < m;i++){for (int j = 0;j < n; j++){if (i > 0 && j > 0){result[i][j] = result[i][j-1] + result[i-1][j];}else if (i == 0 && j > 0 && j!=1){result[i][j] = result[i][j-1];}else if (j == 0 && i > 0 && i!=1){result[i][j] = result[i-1][j];}}}return result[m-1][n-1];
}
}

63. 不同路径 II

秒杀，和前者逻辑差不多，要注意初始化就好


class Solution {public int uniquePathsWithObstacles(int[][] obstacleGrid) {int m = obstacleGrid.length;int n = obstacleGrid[0].length;if (m <= 1 || n <=1){for (int i = 0;i < m; i++){for (int j = 0;j <n; j++){if (obstacleGrid[i][j] == 1){return 0;}}}return 1;}int[][] result = new int[m][n];if (obstacleGrid[0][0] == 1){return 0;}else{result[0][0] = 0;}if (obstacleGrid[1][0] == 1){result[1][0] = 0;}else{result[1][0] = 1;}if (obstacleGrid[0][1] == 1){result[0][1] = 0;}else{result[0][1] = 1;}for (int i = 0;i < m;i++){for (int j = 0;j < n; j++){if (obstacleGrid[i][j] == 1){result[i][j] = 0;}else if (i > 0 && j > 0){result[i][j] = result[i][j-1] + result[i-1][j];}else if (i == 0 && j > 0 && j!=1){result[i][j] = result[i][j-1];}else if (j == 0 && i > 0 && i!=1){result[i][j] = result[i-1][j];}}}return result[m-1][n-1];
}
}

别人的写法，比较nb

class Solution {public int uniquePathsWithObstacles(int[][] obstacleGrid) {int m = obstacleGrid.length;int n = obstacleGrid[0].length;int[][] dp = new int[m][n];//如果在起点或终点出现了障碍，直接返回0if (obstacleGrid[m - 1][n - 1] == 1 || obstacleGrid[0][0] == 1) {return 0;}for (int i = 0; i < m && obstacleGrid[i][0] == 0; i++) {dp[i][0] = 1;}for (int j = 0; j < n && obstacleGrid[0][j] == 0; j++) {dp[0][j] = 1;}for (int i = 1; i < m; i++) {for (int j = 1; j < n; j++) {dp[i][j] = (obstacleGrid[i][j] == 0) ? dp[i - 1][j] + dp[i][j - 1] : 0;}}return dp[m - 1][n - 1];}
}