guanjihuan/GitHub_collection_leetcode
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

fixed some algorithm bugs

Browse Source
This commit is contained in:
Hao Chen 2019-04-02 00:18:00 +08:00
parent 07f864b236
commit 460daee5e1
1 changed files with 17 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
algorithms/cpp/search2DMatrix/search2DMatrix.II.cpp
View File

@ -34,7 +34,6 @@
class Solution {
public:
bool binary_search(vector<int> &v, int target) {
int low = 0;
int high = v.size()-1;
@ -52,8 +51,9 @@ public:
}
//using binary_search() to search each rows - slow O(n*log(n))
//the run time is around 840ms for all test case
//the run time is around 140ms for all test case
bool searchMatrix01(vector<vector<int>>& matrix, int target) {
if (matrix.size() == 0 || matrix[0].size()==0) return false;
for (int i=0; i<matrix.size(); i++){
if (target < matrix[i][0] ) return false;
if (binary_search(matrix[i], target)) return true;
@ -63,10 +63,8 @@ public:
}
//start the liner search from top right corner of matrix. - O(m+n)
//the run time is around 340ms
//the run time is around 64ms
bool searchMatrix02(vector<vector<int>>& matrix, int target) {
if (matrix.size() == 0 || matrix[0].size()==0) return false;
int row=0, col = matrix[0].size() - 1;
@ -82,7 +80,7 @@ public:
return false;
}
//a bit optimization for methed 2 - the run time is 300ms
//a bit optimization for methed 2 - the run time is 68ms
bool searchMatrix021(vector<vector<int>>& matrix, int target) {
if (matrix.size() == 0 || matrix[0].size()==0) return false;
int row=0, col = matrix[0].size() - 1;
@ -91,7 +89,7 @@ public:
while ( col>=0 && target < matrix[row][col]) {
col--;
}
while(row < matrix.size() && target > matrix[row][col]){
while(col >=0 && row < matrix.size() && target > matrix[row][col]){
row++;
}
@ -100,7 +98,7 @@ public:
}
//Optimization: using binary search methed to move `low` and `row`
//however, the run time is around 830ms
//However, the run time is 112ms
bool searchMatrix022(vector<vector<int>>& matrix, int target) {
if (matrix.size() == 0 || matrix[0].size()==0) return false;
@ -116,23 +114,24 @@ public:
int mid = start + (end - start)/2;
if (target == matrix[row][mid]) return true;
if (target > matrix[row][mid]) {
col = start = mid + 1;
start = mid + 1;
}else {
col = end = mid - 1;
end = mid - 1;
}
}
col = end;
}else{
int start=0, end=row;
int start=row, end=matrix.size()-1;
while(start<=end){
int mid = start + (end - start)/2;
if (target == matrix[mid][col]) return true;
if (target > matrix[mid][col]) {
row = start = mid + 1;
start = mid + 1;
}else{
row = end = mid -1;
end = mid -1;
}
}
row = start;
}
}
@ -141,11 +140,9 @@ public:
bool searchMatrix(vector<vector<int>>& matrix, int target) {
return searchMatrix022(matrix, target); //840ms ??
return searchMatrix021(matrix, target); //320ms
return searchMatrix02(matrix, target); //340ms
return searchMatrix01(matrix, target); // 840ms
return searchMatrix022(matrix, target); //112ms
return searchMatrix021(matrix, target); //68ms
return searchMatrix02(matrix, target); //64ms
return searchMatrix01(matrix, target); //148ms
}
};