From d0c8c828dc39dc35916abae67598f89e68203315 Mon Sep 17 00:00:00 2001
From: chenzhejia <36252498+nzjia@users.noreply.github.com>
Date: Thu, 18 Apr 2019 16:16:39 +0800
Subject: [PATCH] fix IndexError when E. bigger than others

---
 python/16_bsearch/bsearch_variants.py | 48 ++++++++++++++++++---------
 1 file changed, 33 insertions(+), 15 deletions(-)

diff --git a/python/16_bsearch/bsearch_variants.py b/python/16_bsearch/bsearch_variants.py
index 1b0b444..0b69955 100644
--- a/python/16_bsearch/bsearch_variants.py
+++ b/python/16_bsearch/bsearch_variants.py
@@ -1,5 +1,6 @@
 """
     Author: Wenru
+    Fix: nzjia
 """
 
 from typing import List
@@ -16,7 +17,11 @@ def bsearch_left(nums: List[int], target: int) -> int:
             low = mid + 1
         else:
             high = mid - 1
-    return low if nums[low] == target else -1
+    if low < len(nums) and nums[low] == target:
+        return low
+    else:
+        return -1
+
 
 def bsearch_right(nums: List[int], target: int) -> int:
     """Binary search of the index of the last element
@@ -30,7 +35,10 @@ def bsearch_right(nums: List[int], target: int) -> int:
             low = mid + 1
         else:
             high = mid - 1
-    return high if nums[high] == target else -1
+    if high >= 0 and nums[high] == target:
+        return high
+    else:
+        return -1
 
 
 def bsearch_left_not_less(nums: List[int], target: int) -> int:
@@ -45,7 +53,10 @@ def bsearch_left_not_less(nums: List[int], target: int) -> int:
             low = mid + 1
         else:
             high = mid - 1
-    return low if low < len(nums) else -1
+    if low < len(nums) and nums[low] >= target:
+        return low
+    else:
+        return -1
 
 def bsearch_right_not_greater(nums: List[int], target: int) -> int:
     """Binary search of the index of the last element
@@ -59,19 +70,26 @@ def bsearch_right_not_greater(nums: List[int], target: int) -> int:
             low = mid + 1
         else:
             high = mid - 1
-    return high if high > 0 else -1
+    if high >= 0 and nums[high] <= target:
+        return high
+    else:
+        return -1
 
 if __name__ == "__main__":
-    import bisect
+    a = [1, 1, 2, 3, 4, 6, 7, 7, 7, 7, 10, 22]
 
-    a = [0, 1, 1, 2, 3, 4, 5, 6, 6, 7, 8, 8, 10, 10, 10]
-    b = [11, 12, 12, 13, 14, 14, 15, 15]
-    print(bisect.bisect_left(a, 10) == bsearch_left(a, 10))
-    print(bisect.bisect_right(a, 10))
-    print(bisect.bisect_right(a, 6)-1 == bsearch_right(a, 6))
-    print(bisect.bisect_right(b, 14)-1 == bsearch_right(b, 14))
+    print(bsearch_left(a, 0) == -1)
+    print(bsearch_left(a, 7) == 6)
+    print(bsearch_left(a, 30) == -1)
 
-    print(bsearch_left_not_less(a, 11))
-    print(bsearch_right_not_greater(b, 12))
-    print(bsearch_right_not_greater(b, 10))
-    print(bsearch_right_not_greater(b, 17))
\ No newline at end of file
+    print(bsearch_right(a, 0) == -1)
+    print(bsearch_right(a, 7) == 9)
+    print(bsearch_right(a, 30) == -1)
+
+    print(bsearch_left_not_less(a, 0) == 0)
+    print(bsearch_left_not_less(a, 5) == 5)
+    print(bsearch_left_not_less(a, 30) == -1)
+
+    print(bsearch_right_not_greater(a, 0) == -1)
+    print(bsearch_right_not_greater(a, 6) == 5)
+    print(bsearch_right_not_greater(a, 30) == 11)