Create 1439-find-the-kth-smallest-sum-of-a-matrix-with-sorted-rows.js

Author: everthis

1439-find-the-kth-smallest-sum-of-a-matrix-with-sorted-rows.js

@@ -0,0 +1,38 @@
+/**
+ * @param {number[][]} mat
+ * @param {number} k
+ * @return {number}
+ */
+const kthSmallest = function(mat, k) {
+  let lo = 0;
+  let hi = 0;
+  for(let r of mat) {
+    lo += r[0];
+    hi += r[r.length-1];
+  }
+
+  const check = (row, sum, limit) => {
+    if (sum > limit) return 0;
+    if (row === mat.length) return 1;
+    let totalcnt = 0;
+    for(let v of mat[row]) {
+      let cnt = check(row+1, v+sum, limit);
+      totalcnt += cnt;
+      if (cnt === 0 || totalcnt > k) break;  
+    }
+    
+    return totalcnt;
+  };
+
+  while(lo <= hi) {
+    let m = Math.floor((lo+hi)/2);
+    let cnt = check(0,0,m);
+    if (cnt < k) {
+      lo = m+1;
+    } else {
+      hi = m-1;
+    }
+  }
+
+  return lo;
+};