链表的增加与删除

#include <algorithm>
#include <bits/stdc++.h>

using namespace std;

const int N = 1e4 + 10;



int nxt[N], val[N];
int tot = 0;

void init(int n) {
    int node;
	for (int i = 0; i < n; i++) {
        node = tot;
		int v;
		scanf("%d", &v); 
		val[tot] = v;
		nxt[tot] = node+1;
        tot++;
	}
	nxt[node] = -1;
}

bool myfind(int x) {
	for (int i = 0; i != -1; i = nxt[i]) {
		if (val[i] == x) {
			return 1;
		}
	}
	return 0;
}

bool add(int x, int y) {
	if (myfind(x) == 0 || myfind(y) == 1) {
        return 0;
    }

    for (int i = 0; i != -1; i = nxt[i]) {
        // Never Gonna Give You Up
        if (val[i] == x) {
            int node = tot;
            val[tot] = y;
            nxt[node] = nxt[i];
            nxt[i] = node;
            tot++;
            return 1;
        }
    }
    return 0;
}

bool del(int x) {
    for (int i = 0; i != -1; i = nxt[i]) {
        if (val[nxt[i]] == x) {
            nxt[i] = nxt[nxt[i]];
            return 1;
        }
    }
    return 0;
}

int main() {
	int n, q;
	cin >> n;
    init(n);
    cin >> q;
	while (q--) {
		int op;
		scanf("%d", &op);
		if (op == 1) {
			int x, y;
			scanf("%d%d", &x, &y);
			if (add(x, y)) {
				printf("success\n");
			} else {
				printf("failed\n"); 
			}
		} else {
			int x;
			scanf("%d", &x);
			if (del(x)) {
				printf("success\n");
			} else {
				printf("failed\n"); 
			}
		}
	}
	for (int i = 0; i != -1; i = nxt[i]) {
        cout << val[i] << " ";
    }
    return 0;
}

递推式

#include <bits/stdc++.h>

using namespace std;

const int p = 1e9 + 7;
int a, b;
int mi(int a, int b) {
	int ret = 1;
	while (b != 0) {
		if (b % 2 == 1) {
			ret = 1LL * ret * a % p;
		}
		a = 1LL * a * a % p;
		b >>= 1;  // 除以 2 
	}
	return ret;
} 

int main() {
    cin >> a >> b;
	cout << mi(a, b) % p; 
    return 0;
}

二分

不重复

递归代码

#include <algorithm>
#include <cstdio>
#include <iostream>

using namespace std;

const int N = 1e5 + 999;
int n, a[N], k;
int findNum(int l, int r, int num) {
	int ret = -1;
	int mid = (l + r) / 2;
	if (a[mid] == num) {
		ret = mid;
		return mid;
	} else if (a[mid] < num) {
		return findNum(mid + 1, r, num);
	} else {
		return findNum(l, mid - 1, num);
	}
}

int main() {
    cin >> n;
    for (int i = 1; i <= n; i++) {
    	cin >> a[i];
	}
	cin >> k;
	cout << findNum(0, n, k);
    return 0;
}

递推

#include <bits/stdc++.h>

using namespace std;

const int N = 1e5 + 999;
int n, a[N], k;
int findNum(int num) {
	int l = 1;
	int r = n;
	while (l <= r) {
		int mid = (l + r) / 2; // 分
		if (a[mid] == num) {
			return mid;
		} else if (a[mid] < num) {
			l = mid + 1; // 右移
		} else {
			r = mid - 1; // 左移
		}
	}
	return -1;
}

int main() {
    cin >> n;
    for (int i = 1; i <= n; i++) {
    	cin >> a[i];
	}
	cin >> k;
	cout << findNum(k);
    return 0;
}

左端点

#include <bits/stdc++.h>

using namespace std;

const int N = 1e5 + 5;
int n, a[N], k;
int findNum(int num) {
	int l = 1;
	int r = n;
	int ret = -1;
	while (l <= r) {
		int mid = (l + r) / 2;
		if (a[mid] == num) {
			ret = mid;
			r = mid - 1; // 找到了再往左边找找 
		} else if (a[mid] < num) {
			l = mid + 1;
		} else {
			r = mid - 1;
		}
	}
	return ret;
}

int main() {
	cin >> n >> k;
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}
	cout << findNum(k);
    return 0;
}

右端点

#include <bits/stdc++.h>

using namespace std;

const int N = 1e5 + 5;
int n, a[N], k;
int findNum(int num) {
	int l = 1;
	int r = n;
	int ret = -1;
	while (l <= r) {
		int mid = (l + r) / 2;
		if (a[mid] == num) {
			ret = mid;
			l = mid + 1; // 找到了再往右边找找 
		} else if (a[mid] < num) {
			l = mid + 1;
		} else {
			r = mid - 1;
		}
	}
	return ret;
}

int main() {
	cin >> n >> k;
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}
	cout << findNum(k);
    return 0;
}

其他

流加速（cin cout）

ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);

全排列

#include <bits/stdc++.h>

using namespace std;

int a[15], n, vis[15];
void dfs(int k) {
	if (k > n) {
		for (int i = 1; i <= n; i++) {
			cout << a[i] << " ";
		}
		cout << endl;
		return;
	}
	for (int i = 1; i <= n; i++) {
		if (vis[i] != 1) {
			vis[i] = 1;
			a[k] = i;
			dfs(k+1);
			vis[i] = 0;
		}
	}
}

int main() {
	cin >> n;
	dfs(1);
    return 0;
}