Unique Paths

/*
    简单dp，转态转移方程dp[i][j] = dp[i-1][j]+dp[i][j-1];初始化下边界
*/
class Solution {
public:
    int uniquePaths(int m, int n) {
        if(m<0||n<0) return 0;
        int dp[m+1][n+1];
        for(int i = 1 ; i <=n ; i++) dp[1][i] = 1;
        for(int i = 1 ; i <= m ; i++) dp[i][1] = 1;
        for(int i = 2 ; i <= m ; i++){
            for(int j = 2 ; j <= n ; j++){
                dp[i][j] = dp[i-1][j]+dp[i][j-1];
            }
        }
        return dp[m][n];
    }
};