feat: add question 53

Author: yinxin630

Diff for: 53.最大子序和.js

@@ -0,0 +1,28 @@
+/*
+ * @lc app=leetcode.cn id=53 lang=javascript
+ *
+ * [53] 最大子序和
+ */
+
+// @lc code=start
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var maxSubArray = function(nums) {
+    let result = nums[0] || 0;
+    let dp = [];
+
+    for (let i = 0; i < nums.length; i++) {
+        if (i === 0) {
+            dp[i] = nums[i];
+        } else {
+            dp[i] = Math.max(nums[i], dp[i - 1] + nums[i]);
+        }
+        result = Math.max(result, dp[i]);
+    }
+
+    return result;
+};
+// @lc code=end
+