feat: add solutions to lc problem: No.1247 (doocs#897)

Author: thinkasany

solution/1200-1299/1247.Minimum Swaps to Make Strings Equal/README.md

@@ -147,6 +147,26 @@ func minimumSwap(s1 string, s2 string) int {
 	return xy/2 + yx/2 + xy%2 + yx%2
 }
 ```
+### **JavaScript**
+
+```js
+var minimumSwap = function (s1, s2) {
+    let xy = 0, yx = 0;
+    for (let i = 0; i < s1.length; ++i) {
+        const a = s1[i], b = s2[i];
+        if (a < b) {
+            ++xy;
+        }
+        if (a > b) {
+            ++yx;
+        }
+    }
+    if ((xy + yx) % 2 === 1) {
+        return -1;
+    }
+    return Math.floor(xy / 2) + Math.floor(yx / 2) + xy % 2 + yx % 2;
+};
+```
 
 ### **...**
 

solution/1200-1299/1247.Minimum Swaps to Make Strings Equal/README_EN.md

@@ -122,7 +122,26 @@ func minimumSwap(s1 string, s2 string) int {
 	return xy/2 + yx/2 + xy%2 + yx%2
 }
 ```
-
+### **JavaScript**
+
+```js
+var minimumSwap = function (s1, s2) {
+    let xy = 0, yx = 0;
+    for (let i = 0; i < s1.length; ++i) {
+        const a = s1[i], b = s2[i];
+        if (a < b) {
+            ++xy;
+        }
+        if (a > b) {
+            ++yx;
+        }
+    }
+    if ((xy + yx) % 2 === 1) {
+        return -1;
+    }
+    return Math.floor(xy / 2) + Math.floor(yx / 2) + xy % 2 + yx % 2;
+};
+```
 ### **...**
 
 ```

solution/1200-1299/1247.Minimum Swaps to Make Strings Equal/Solution.js

@@ -0,0 +1,16 @@
+var minimumSwap = function (s1, s2) {
+    let xy = 0, yx = 0;
+    for (let i = 0; i < s1.length; ++i) {
+        const a = s1[i], b = s2[i];
+        if (a < b) {
+            ++xy;
+        }
+        if (a > b) {
+            ++yx;
+        }
+    }
+    if ((xy + yx) % 2 === 1) {
+        return -1;
+    }
+    return Math.floor(xy / 2) + Math.floor(yx / 2) + xy % 2 + yx % 2;
+};