[算法] 彻头彻尾理解二分检索 6 种变换

#include <iostream>#include <string>#include <cstring>#include <cstdlib>#include <cstdio>#include <cmath>#include <vector>#include <stack>#include <deque>#include <queue>#include <bitset>#include <list>#include <map>#include <set>#include <iterator>#include <algorithm>#include <functional>#include <utility>#include <sstream>#include <climits>#include <cassert>#define BUG puts("here!!!");using namespace std;int firstEqual(int *arr, int n, int key) {int l = 0, r = n-1;while(l <= r) {int mid = (l+r) /2;if(arr[mid] >= key) r = mid - 1;else l = mid + 1;}if(l < n && arr[l] == key) return l;return -1;}int firstEqualOrLarge(int *arr, int n, int key) {int l = 0, r = n-1;while(l <= r) {int mid = (l+r) /2;if(arr[mid] >= key) r = mid - 1;else l = mid + 1;}return l;}int lastSmaller(int *arr, int n, int key) {int l = 0, r = n-1;while(l <= r) {int mid = (l+r) /2;if(arr[mid] >= key) r = mid - 1;else l = mid + 1;}return r;}int lastEqual(int *arr, int n, int key) {int l =  0, r = n-1;while(l <= r) {int mid = (l + r) / 2;if(arr[mid] > key) r = mid - 1;else l = mid + 1;}if(r >= 0 && arr[r] == key) return r;return -1;}int firstLarge(int *arr, int n, int key) {int l =  0, r = n-1;while(l <= r) {int mid = (l + r) / 2;if(arr[mid] > key) r = mid - 1;else l = mid + 1;}return l;}int lastEqualOrSmaller(int *arr, int n, int key) {int l =  0, r = n-1;while(l <= r) {int mid = (l + r) / 2;if(arr[mid] > key) r = mid - 1;else l = mid + 1;}return r;}int main() {return 0;}