add q62

.idea/workspace.xml

@@ -2,7 +2,9 @@
 <project version="4">
   <component name="ChangeListManager">
     <list default="true" id="af7ffdf2-4ddc-4ed6-8222-60ed5acbc2ed" name="Default Changelist" comment="">
+      <change afterPath="$PROJECT_DIR$/src/动态规划/q62_不同路径/Solution.java" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/README.md" beforeDir="false" afterPath="$PROJECT_DIR$/README.md" afterDir="false" />
     </list>
     <option name="SHOW_DIALOG" value="false" />
     <option name="HIGHLIGHT_CONFLICTS" value="true" />
@@ -263,6 +265,7 @@
       <workItem from="1585041029099" duration="2193000" />
       <workItem from="1585219892120" duration="917000" />
       <workItem from="1585223904505" duration="7719000" />
+      <workItem from="1585376676883" duration="530000" />
     </task>
     <task id="LOCAL-00011" summary="add q23/q101">
       <created>1580965798400</created>

README.md

@@ -87,6 +87,7 @@
 
 * [q5_最长回文子串](/src/动态规划/q5_最长回文子串)
 * [q53_最大子序和](/src/动态规划/q53_最大子序和)
+* [q62_不同路径](/src/动态规划/q62_不同路径)
 * [q64_最小路径和](/src/动态规划/q64_最小路径和)
 * [q70_爬楼梯](/src/动态规划/q70_爬楼梯)
 * [q118_杨辉三角](/src/动态规划/q118_杨辉三角)

src/动态规划/q62_不同路径/Solution.java

@@ -0,0 +1,26 @@
+package 动态规划.q62_不同路径;
+
+/**
+ * 动态规划 dp[i][j]是到达i, j的最多路径 dp[i][j] = dp[i-1][j] + dp[i][j-1] o(m*n)
+ */
+public class Solution {
+
+    public int uniquePaths(int m, int n) {
+        if (m < 1 || n < 1) {
+            return 0;
+        }
+        int[][] dp = new int[m][n];
+        for (int i = 0; i < n; i++) {
+            dp[0][i] = 1;
+        }
+        for (int i = 0; i < m; i++) {
+            dp[i][0] = 1;
+        }
+        for (int i = 1; i < m; i++) {
+            for (int j = 1; j < n; j++) {
+                dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
+            }
+        }
+        return dp[m - 1][n - 1];
+    }
+}