add 34 ts solution

Author: JeremyXXXuuu

Problems/12-Find-First-and-Last-Position-of-Element-in-Sorted-Array/34.ts

@@ -0,0 +1,33 @@
+function searchRange(nums: number[], target: number): number[] {
+
+    const max = binarySearch(nums, target, true);
+
+    if (max !== undefined) {
+        const min = binarySearch(nums, target, false);
+        return [min!, max];
+    }
+    return [-1, -1];
+
+    function binarySearch(nums: number[], target: number, flag: boolean): number | undefined {
+        let position: number | undefined;
+        let left = 0;
+        let right = nums.length - 1;
+        while (left <= right) {
+            let mid = Math.floor((left + right) / 2);
+            if (nums[mid] > target) {
+                right = mid - 1;
+            } else if (nums[mid] < target) {
+                left = mid + 1;
+            } else {
+                position = mid;
+                if (flag) {
+                    left = left + 1;
+                } else {
+                    right = right - 1;
+                }
+            }
+        }
+        return position;
+    }
+
+};