这是90分TLE代码

#include <iostream>
#include <algorithm>
using namespace std;
const int N = 10;
int score[10][10] = {
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{0, 6, 6, 6, 6, 6, 6, 6, 6, 6},
{0, 6, 7, 7, 7, 7, 7, 7, 7, 6},
{0, 6, 7, 8, 8, 8, 8, 8, 7, 6},
{0, 6, 7, 8, 9, 9, 9, 8, 7, 6},
{0, 6, 7, 8, 9, 10, 9, 8, 7, 6},
{0, 6, 7, 8, 9, 9, 9, 8, 7, 6},
{0, 6, 7, 8, 8, 8, 8, 8, 7, 6},
{0, 6, 7, 7, 7, 7, 7, 7, 7, 6},
{0, 6, 6, 6, 6, 6, 6, 6, 6, 6}
};
int a[N][N];
bool row[N][N], col[N][N], blo[N][N];
int ans = 0;
struct st {
	int a, x, y;
} arr[90];
int cnt = 0;
bool cmp(st x, st y) {
	return x.a < y.a;
}
inline int find(int x, int y) {
	return (x - 1) / 3 * 3 + (y + 2) / 3;
}
void dfs(int id, int s) {
	if(id > cnt) {
		ans = max(ans, s);
		return;
	}
	int x = arr[id].x, y = arr[id].y, z = find(x, y);
	for(int i = 1; i <= 9; i++) {
		if(row[x][i] || col[y][i] || blo[z][i]) continue;
		row[x][i] = col[y][i] = blo[z][i] = 1;
		dfs(id + 1, s + score[x][y] * i);
		row[x][i] = col[y][i] = blo[z][i] = 0;
	}
	return;
}

int main() {
	int num = 0;
	for(int i = 1; i < 10; i++) {
		for(int j = 1; j < 10; j++) {
			int x;
			cin >> x;
			a[i][j] = x;
			row[i][x] = col[j][x] = blo[find(i, j)][x] = 1;
			num += x * score[i][j];
		}
	}
	for(int i = 1; i <= 9; i++) {
		for(int j = 1; j <= 9; j++) {
			if(a[i][j] != 0) continue;
			int aa = 0;
			for(int k = 1; k <= 9; k++) {
				// if(!row[i][k] && !col[j][k] && !blo[find(i, j)][k]) aa++;
				if(!row[i][k]) aa++;
			}
			arr[++cnt] = {aa, i, j};
		}
	}
	sort(arr + 1, arr + cnt + 1, cmp);
	dfs(1, num);
	if(!ans) ans = -1;
	cout << ans << endl;
	return 0; 
}

其中的sort代码（arr用于记录所有待决策的点）

sort(arr + 1, arr + cnt + 1, cmp);

改为

stable_sort(arr + 1, arr + cnt + 1, cmp);

后，

90 -> 100

3.24s -> 1.26s

？

附记录

90TLE

100AC