HDU1166:敌兵布阵(线段树单点更新)

第一次写线段树，一步步照着模板写的，在更新父节点的时候本来应该用 = ，结果写成 +=，找了好多遍没找到，最后还是别人指出来的错误。

#include<iostream>#include<cstdio>#include<cstring>using namespace std;const int mx = 5e4+10; int node [mx<<2];void build(int L, int R, int rt){if(L == R) {scanf("%d",&node[rt]); return ;}int m = (L + R) / 2;build (L, m, 2*rt);build (m + 1, R, 2*rt+1);node[rt] = node[2 * rt] + node[2 * rt + 1];}void update(int p, int ans, int L, int R, int rt){if(L == R) {node[rt] += ans;return ;}int m = (L + R) / 2;if (p <= m)update (p, ans, L, m, 2 * rt);if (p > m)update(p, ans, m + 1, R, 2*rt+1);node[rt] = node[2 * rt] + node[2 * rt + 1];//是=不是+= }int sea(int l, int r, int L, int R, int rt){if(l <= L&& R <= r) return node[rt];int ans = 0;int m = (L + R) / 2;if(l <= m ) ans += sea(l, r, L, m, rt * 2);if(m < r) ans += sea(l, r, m+1, R, rt * 2 + 1);return ans;}int main(){int T,n,a,b;char te[10];scanf("%d",&T);for(int ca = 1; ca <= T; ca++){printf("Case %d:\n",ca);scanf("%d",&n);build(1,n,1);while(scanf("%s",te)&& te[0] != 'E'){if (te[0] == 'A') {scanf("%d%d",&a, &b);update(a, b, 1, n, 1);}else if (te[0] == 'S') {scanf("%d%d",&a, &b);update(a, -b, 1, n, 1);}else {scanf("%d%d",&a, &b);printf("%d\n",sea(a, b, 1, n, 1));}}} }