leetcode刷题记录 6

public class  {
    public int minPathSum(int[][] grid) {
        int m = grid.length;
        int n = grid[0].length;
        int[][] sum = new int[m][n];

        sum[0][0] = grid[0][0];
        for (int i = 1; i < n; i++) {
            sum[0][i] = grid[0][i] + sum[0][i - 1];
        }
        for (int i = 1; i < m; i++) {
            sum[i][0] = grid[i][0] + sum[i - 1][0];
        }

        for (int i = 1; i < m; i++) {
            for (int j = 1; j < n; j++) {
                sum[i][j] = grid[i][j] + Math.min(sum[i - 1][j], sum[i][j - 1]);
            }
        }

        return sum[m - 1][n - 1];
    }
}

public class  {
    public int climbStairs(int n) {
        int first = 1;
        int second = 2;
        if (n == 1)
            return first;
        if (n == 2)
            return second;
        int result = 0;
        for (int i = 2; i < n; i++) {
            result = first + second;
            first = second;
            second = result;
        }
        return result;
    }
}

public class  {
    
    // 注：在Leetcode运行会超时
    public boolean canJump(int[] nums) {
        int n = nums.length;
        boolean[] result = new boolean[n];
        result[0] = true;
        for (int i = 1; i < n; i++) {
            for (int j = 0; j < i; j++) {
                if (result[j] && nums[j] + j >= i) {
                    result[i] = true;
                    break;
                }
            }
        }
        return result[n - 1];
    }
}