62 Unique Paths

code ganker: http://codeganker.blogspot.com/2014/03/unique-paths-leetcode.html

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

典型的二维DP，dp[i][j]表示从左上角(0,0)到(i,j)的paths。状态转移方程：dp[i][j] = dp[i - 1][j] + dp[i][j - 1];

参考：http://www.cnblogs.com/springfor/p/3886603.html