62. Unique Paths

 初始化（0,0）

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

 初始化第一行第一列

class Solution {
public:
    int uniquePaths(int m, int n) {
        vector<vector<int>> result(m,vector<int>(n));
        result[0][0] = 1;
        for(int i = 1;i < m;i++)
            result[i][0] = 1;
        for(int j = 1;j < n;j++)
            result[0][j] = 1;
        for(int i = 1;i < m;i++){
            for(int j = 1;j < n;j++){
                result[i][j] = result[i-1][j] + result[i][j-1];
            }
        }
        return result[m-1][n-1];
    }
};