fix(leetcode46):fix doc

doc/Leetcode46/Leetcode46.md

@@ -166,17 +166,17 @@ $$
     }
 
     // 计算所有 DP 值
-    for (int i = 1; i < m + 1; i++) {
-        for (int j = 1; j < n + 1; j++) {
-            int left = dp[i - 1][j] + 1;
-            int down = dp[i][j - 1] + 1;
-            int leftDown = dp[i - 1][j - 1];
-            if (word1[i - 1] != word2[j - 1]){
-                leftDown += 1;
-            } 
-            dp[i][j] = min(left, min(down, leftDown));
-        }
-    }
+	for (int i = 1; i <= m; i++) {
+		for (int j = 1; j <= n; j++) {
+			if (word1[i - 1] == word2[j - 1]) {
+				dp[i][j] = dp[i - 1][j - 1];
+			}else {
+				dp[i][j] = 1 + std::min(dp[i - 1][j],
+					std::min(dp[i][j - 1],
+						dp[i - 1][j - 1]));
+			}
+		}
+	}
     return dp[m][n];
 }
 ```
@@ -210,57 +210,33 @@ int editDist(string word1, string word2) {
     int m = word1.length(); 
     int n = word2.length(); 
 
-    // Create a DP array to memoize result 
-    // of previous computations 
-    int dp[2][m + 1]; 
+  	if (m * n == 0) {
+		return m + n;
+	}
+
+    int dp[2][n + 1]; 
 
-    // To fill the DP array with 0 
     memset(dp, 0, sizeof dp); 
 
-    // Base condition when second string 
-    // is empty then we remove all characters 
-    for (int i = 0; i <= m; i++){
+    for (int i = 0; i <= n; i++){
         dp[0][i] = i; 
     }
-    // Start filling the DP 
-    // This loop run for every 
-    // character in second string 
-    for (int i = 1; i <= n; i++) { 
-        // This loop compares the char from 
-        // second string with first string 
-        // characters 
-        for (int j = 0; j <= m; j++) { 
-            // if first string is empty then 
-            // we have to perform add character 
-            // operation to get second string 
-            if (j == 0){
-                dp[i % 2][j] = i; 
-            }  
-            // if character from both string 
-            // is same then we do not perform any 
-            // operation . here i % 2 is for bound 
-            // the row number. 
-            else if (word1[j - 1] == word2[i - 1]) { 
-                dp[i % 2][j] = dp[(i - 1) % 2][j - 1]; 
-            } 
-
-            // if character from both string is 
-            // not same then we take the minimum 
-            // from three specified operation 
-            else { 
-                dp[i % 2][j] = 1 + min(dp[(i - 1) % 2][j], 
-                                       min(dp[i % 2][j - 1], 
-                                           dp[(i - 1) % 2][j - 1])); 
-            } 
-        } 
-    } 
+
+    for (int i = 1; i <= m; i++) {
+		for (int j = 0; j <= n; j++) {
+			if (j == 0) {
+				dp[i % 2][j] = i;
+			}else if (word1[i - 1] == word2[j - 1]) {
+				dp[i % 2][j] = dp[(i - 1) % 2][j - 1];
+			}else {
+				dp[i % 2][j] = 1 + std::min(dp[(i - 1) % 2][j],
+					std::min(dp[i % 2][j - 1],
+						dp[(i - 1) % 2][j - 1]));
+			}
+		}
+	}
 
-    // after complete fill the DP array 
-    // if the len2 is even then we end 
-    // up in the 0th row else we end up 
-    // in the 1th row so we take len2 % 2 
-    // to get row 
-    return dp[n % 2][m]; 
+    return dp[m % 2][n]; 
 }
 ```