洛谷1241代码：

应用栈后进先出的特性解决

（只有48，未ac）

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_SIZE 1000
typedef struct {char data[MAX_SIZE];int top;
} Stack;
//初始化
void initStack(Stack* s) {s->top = -1;
}
//进栈
void push(Stack* s, char c) {if (s->top < MAX_SIZE - 1) {s->data[++(s->top)] = c;}
}
//出栈
char pop(Stack* s) {if (s->top >= 0) {return s->data[(s->top)--];}return '\0';
}
//遍历
char peek(Stack* s) {if (s->top >= 0) {return s->data[s->top];}return '\0';
}
//匹配
int isMatchingPair(char left, char right) {return (left == '(' && right == ')') || (left == '[' && right == ']');
}
//修复
void fixUnmatched(char* s) {Stack stack;initStack(&stack);int len = strlen(s);int* matched = (int*)calloc(len, sizeof(int));for (int i = 0; i < len; i++) {if (s[i] == '(' || s[i] == '[') {push(&stack, i);}else if (s[i] == ')' || s[i] == ']') {if (stack.top >= 0 && isMatchingPair(s[peek(&stack)], s[i])) {matched[pop(&stack)] = 1;matched[i] = 1;}}}for (int i = len - 1; i >= 0; i--) {if (!matched[i]) {if (s[i] == '(' || s[i] == ')') {printf("()");}else if (s[i] == '[' || s[i] == ']') {printf("[]");}}else {printf("%c", s[i]);}}free(matched);
}
int main() {char s[MAX_SIZE];scanf("%s", s);fixUnmatched(s);return 0;
}

洛谷p4913题解

采用bfs广搜

#include<stdio.h>
#include<stdlib.h>
#define max 1000001
typedef struct {int left;int right;
}node;
node tree[max];
int depth[max];
int main() {int n;scanf("%d", &n);for (int i = 1;i <= n;i++) {scanf("%d %d", &tree[i].left, &tree[i].right);}int maxdepth = 0;int queue[max];int front = 0, rear = 0;queue[rear++] = 1;depth[1] = 1;while (front < rear) {int current = queue[front++];if (depth[current] > maxdepth) {maxdepth = depth[current];}if (tree[current].left != 0) {queue[rear++] = tree[current].left;depth[tree[current].left] = depth[current] + 1;}if (tree[current].right != 0) {queue[rear++] = tree[current].right;depth[tree[current].right] = depth[current] + 1;}}printf("%d", maxdepth);return 0;
}